[Feature] Implement options menu and reading/writing values from/to the SRAM (#449)

* background

* Implement Options button

* Update main menu artwork

* add options menu tiles

* prepare options menu handling

* incorporate main menu refactor

* toto

* add all menu interactions

* do not reset selection_x in main_menu

* options struct

* fix rebase from ricfehr3's repo

* Implement high contrast cards

* Save/Load options values to SRAM

* load options on game_init and validate data within the load_options function

* Get changes from ricfehr3's PR

* recover fix for glitched ace

* clang format

* clang format

* clang format

* Save 500B of image data by using only minimal set of tiles instead of keeping final window in source file

* clang format

* clang format

* Implement Options button

* Update main menu artwork

* progress, leaving it alone for now until discussion

* make game_vars an extern

* Move options vars into their own struct

* rollback previous commit

* Implement save validation. Version check to come

* implement data validity + version check for game saves

* clang format

* Save position in rng sequence for consistent run after load

* fix rebase issues

* fix rebase issue

* remove unused/duplicate define

* Oops, made a mistake when testing PR #424

* encode high contrast palette into an image, and load it at game_start

* document save.c/h and correct typos

* correct alignment

* game speed and high contrast buttons working

* small cleanup

* sliders also work again now

* clang format

* Moved balatro_version extern declaration to version.h file

* removed unsused variable

* make showing ROM version a toggle

* move ante, round and money to the GameVariables struct

* Rename SaveCheckInfo struct to SaveHeader for clarity

* Add SaveHeader struct explanation

* clang format

* Revert unnecessary tileset optimization

* SFX now follows the sound volume slider

* clang format

* Music now follows volume slider

* Changed volume slider increment from 5 to 20 to avoid having the music sound too rough under 20% volume

* refactor main_menu.c to use SelectionGrid and Button structs

* clang format

* make a "new" save button so we don't save during the state transition

* clang format

* Reduced state transition flicker by only changing affine background to a different one

* Fix loading game too late in game init sequence

* First batch of suggestions from @MeirGavish

* Remove unnecessary intermediary buffers for high contrast palette swapping

* comment row warp hack for button input

* Add some of Copilot's suggestions

* rename balatro_version into gbalatro_version for rebranding reasons + version display erase screen fix

* remove unnecessary NULL check on `on_selection_changed` method

* implement small game speed arrow buttons animation

* factorize some code

* remove unnecessary data validation in load_game(), since we already checked the header

* Implement @MeirGavish 's suggestion regarding splitting the huge `on_update` function

* clang format

* implement @ricfehr3 's suggestion about keeping last selected button instead of using an obscure `on_boot` boolean

* Apply @ricfehr3's suggestions

* fix clang-format flags

---------

Co-authored-by: MathisMartin31 <mathis.martin31@gmail.com>

Doxyfile

@@ -572,7 +572,7 @@ EXTRACT_PACKAGE        = NO
 # included in the documentation.
 # The default value is: NO.
 
-EXTRACT_STATIC         = NO
+EXTRACT_STATIC         = YES
 
 # If the EXTRACT_LOCAL_CLASSES tag is set to YES, classes (and structs) defined
 # locally in source files will be included in the documentation. If set to NO,
@@ -588,7 +588,7 @@ EXTRACT_LOCAL_CLASSES  = YES
 # included.
 # The default value is: NO.
 
-EXTRACT_LOCAL_METHODS  = NO
+EXTRACT_LOCAL_METHODS  = YES
 
 # If this flag is set to YES, the members of anonymous namespaces will be
 # extracted and appear in the documentation as a namespace called
@@ -3023,3 +3023,4 @@ MSCFILE_DIRS           =
 EXCLUDE = build tests graphics audio doc scripts
 
 USE_MDFILE_AS_MAINPAGE = CONTRIBUTING.md
+

Makefile

@@ -55,7 +55,7 @@ CFLAGS	+=	$(INCLUDE)
 CXXFLAGS	:=	$(CFLAGS) -fno-rtti -fno-exceptions
 
 ASFLAGS	:=	-g $(ARCH)
-LDFLAGS	=	-g $(ARCH) -Wl,-Map,$(notdir $*.map),--undefined=balatro_version
+LDFLAGS	=	-g $(ARCH) -Wl,-Map,$(notdir $*.map),--undefined=gbalatro_version
 
 #---------------------------------------------------------------------------------
 # any extra libraries we wish to link with the project

graphics/background_options_menu_gfx.grit

@@ -0,0 +1 @@
+-gB8 -mR8 -mLs -mRtf -pn 160

graphics/deck_gfx.grit

@@ -1 +1 @@
--gB4 -Mw4 -Mh4 -m!
+-gB4 -Mw4 -Mh4 -m! -pn 16

graphics/high_contrast_deck_pal_gfx.grit

@@ -0,0 +1 @@
+-gB4 -g! -m! -pn 16

include/affine_background.h

@@ -33,6 +33,13 @@
  */
 enum AffineBackgroundID
 {
+    /**
+     * @brief Display background for the initial splash screen.
+     *
+     * Signifies that no background is currently in use.
+     */
+    AFFINE_BG_NONE,
+
     /**
      * @brief Display background for main menu.
      *

include/audio_utils.h

@@ -9,10 +9,16 @@
 #include <mm_types.h>
 
 /**
- * @def MM_FULL_VOLUME
+ * @def MM_MODULE_FULL_VOLUME
+ * @brief The maximum volume for maxmod module volume (main theme)
+ */
+#define MM_MODULE_FULL_VOLUME 1024
+
+/**
+ * @def MM_SFX_FULL_VOLUME
  * @brief The maximum volume for maxmod mm_sound_effect.volume
  */
-#define MM_FULL_VOLUME 255
+#define MM_SFX_FULL_VOLUME 255
 
 /**
  * @def MM_PAN_CENTER
@@ -32,7 +38,7 @@
  * @def SFX_DEFAULT_VOLUME
  * @brief Default volume for sound effects
  */
-#define SFX_DEFAULT_VOLUME MM_FULL_VOLUME
+#define SFX_DEFAULT_VOLUME MM_SFX_FULL_VOLUME
 
 /**
  * @def SFX_DEFAULT_PAN

include/button.h

@@ -11,7 +11,7 @@
 
 #define BTN_HIGHLIGHT_COLOR 0xFFFF
 
-#define BUTTON_SFX_VOLUME 154 // 60% of MM_FULL_VOLUME
+#define BUTTON_SFX_VOLUME 154 // 60% of MM_SFX_FULL_VOLUME
 
 /**
  * @brief The function to be called when the button is pressed

include/card.h

@@ -56,6 +56,7 @@ typedef struct CardObject
 
 // Card functions
 void card_init();
+void toggle_high_contrast_cards(bool enable);
 
 // Card methods
 Card* card_new(u8 suit, u8 rank);

include/def_state_info_table.h

@@ -1,12 +1,13 @@
 // clang-format off
 // (stateEnum, on_init, on_update, on_exit)
-DEF_STATE_INFO(GAME_STATE_SPLASH_SCREEN, splash_screen_on_init, splash_screen_on_update, splash_screen_on_exit) 
-DEF_STATE_INFO(GAME_STATE_MAIN_MENU, game_main_menu_on_init, game_main_menu_on_update, game_main_menu_on_exit)
-DEF_STATE_INFO(GAME_STATE_GAME_START, noop, game_start, noop)
-DEF_STATE_INFO(GAME_STATE_PLAYING, game_round_on_init, game_playing_on_update, noop)
-DEF_STATE_INFO(GAME_STATE_ROUND_END, noop, game_round_end_on_update, game_round_end_on_exit)
-DEF_STATE_INFO(GAME_STATE_SHOP, noop, game_shop_on_update, game_shop_on_exit)
-DEF_STATE_INFO(GAME_STATE_BLIND_SELECT, game_blind_select_on_init, game_blind_select_on_update, game_blind_select_on_exit)
-DEF_STATE_INFO(GAME_STATE_LOSE, game_lose_on_init, game_lose_on_update, game_over_on_exit)
-DEF_STATE_INFO(GAME_STATE_WIN, game_win_on_init, game_win_on_update, game_over_on_exit)
+DEF_STATE_INFO(GAME_STATE_SPLASH_SCREEN, splash_screen_on_init,     splash_screen_on_update,     splash_screen_on_exit    )
+DEF_STATE_INFO(GAME_STATE_MAIN_MENU,     game_main_menu_on_init,    game_main_menu_on_update,    game_main_menu_on_exit   )
+DEF_STATE_INFO(GAME_STATE_OPTIONS_MENU,  game_options_menu_on_init, game_options_menu_on_update, game_options_menu_on_exit)
+DEF_STATE_INFO(GAME_STATE_GAME_START,    noop,                      game_start,                  noop                     )
+DEF_STATE_INFO(GAME_STATE_PLAYING,       game_round_on_init,        game_playing_on_update,      noop                     )
+DEF_STATE_INFO(GAME_STATE_ROUND_END,     noop,                      game_round_end_on_update,    game_round_end_on_exit   )
+DEF_STATE_INFO(GAME_STATE_SHOP,          noop,                      game_shop_on_update,         game_shop_on_exit        )
+DEF_STATE_INFO(GAME_STATE_BLIND_SELECT,  game_blind_select_on_init, game_blind_select_on_update, game_blind_select_on_exit)
+DEF_STATE_INFO(GAME_STATE_LOSE,          game_lose_on_init,         game_lose_on_update,         game_over_on_exit        )
+DEF_STATE_INFO(GAME_STATE_WIN,           game_win_on_init,          game_win_on_update,          game_over_on_exit        )
 // clang-format on

include/game.h

@@ -1,6 +1,7 @@
 #ifndef GAME_H
 #define GAME_H
 
+#include "blind.h"
 #include "game/common_ui.h"
 #include "game_variables.h"
 
@@ -13,7 +14,7 @@ extern GameVariables g_game_vars;
 #define MAX_JOKERS_HELD_SIZE 5 // This doesn't account for negatives right now.
 #define MAX_SHOP_JOKERS      2 // TODO: Make this dynamic and allow for other items besides jokers
 #define MAX_SELECTION_SIZE   5
-#define FRAMES(x)            (((x) + game_speed - 1) / game_speed)
+#define FRAMES(x)            (((x) + (g_game_vars.game_speed) - 1) / (g_game_vars.game_speed))
 
 // TODO: Can make these dynamic to support interest-related jokers and vouchers
 #define MAX_INTEREST   5
@@ -123,7 +124,7 @@ typedef struct ContainedHandTypes
 } ContainedHandTypes;
 // clang-format on
 
-typedef void (*GameStateCallback)();
+typedef void (*GameStateCallback)(void);
 
 typedef struct
 {
@@ -158,17 +159,16 @@ int get_num_hands_remaining(void);
 
 u32 get_chips(void);
 void set_chips(u32 new_chips);
-void display_chips();
+void display_chips(void);
 u32 get_mult(void);
 void set_mult(u32 new_mult);
-void display_mult();
-int get_money(void);
-void set_money(int new_money);
-void display_money();
+void display_mult(void);
+void display_money(void);
 void set_retrigger(bool new_retrigger);
+enum BlindType get_current_blind(void);
+enum BlindType get_next_boss_blind(void);
 
-int get_game_speed(void);
-void set_game_speed(int new_game_speed);
+u32 get_rand(void);
 
 // joker specific functions
 bool is_shortcut_joker_active(void);

include/game/common_ui.h

@@ -17,6 +17,7 @@ enum BackgroundId
     BG_ROUND_END,
     BG_SHOP,
     BG_BLIND_SELECT,
+    BG_OPTIONS_MENU,
     BG_MAIN_MENU
 };
 

include/game/main_menu.h

@@ -15,23 +15,17 @@ void game_main_menu_change_background(void);
 
 /**
  * @brief Main menu state initialization
- *
- * @param vars passed @ref GameVariables struct
  */
 void game_main_menu_on_init(void);
 
 /**
  * @brief Main menu state update
- *
- * @param vars passed @ref GameVariables struct
  */
 void game_main_menu_on_update(void);
 
 /**
  * @brief Main menu cleanup (called when transitioning to game start)
- *
- * @param vars passed @ref GameVariables struct
  */
 void game_main_menu_on_exit(void);
 
-#endif // GAME_MAIN_MENU_H
+#endif // GAME_MAIN_MENU_H

include/game/options_menu.h

@@ -0,0 +1,31 @@
+/**
+ * @file options_menu.h
+ *
+ * @brief Options menu state functions.
+ */
+#ifndef GAME_OPTIONS_MENU_H
+#define GAME_OPTIONS_MENU_H
+
+#include "game_variables.h"
+
+/**
+ * @brief Change the options menu background
+ */
+void game_options_menu_change_background(void);
+
+/**
+ * @brief Options menu state initialization
+ */
+void game_options_menu_on_init(void);
+
+/**
+ * @brief Options menu state update
+ */
+void game_options_menu_on_update(void);
+
+/**
+ * @brief Options menu cleanup (called when going back to main menu)
+ */
+void game_options_menu_on_exit(void);
+
+#endif // GAME_OPTIONS_MENU_H

include/game_variables.h

@@ -8,6 +8,19 @@
 
 #include <tonc.h>
 
+#define GAME_SPEED_MIN 1
+#define GAME_SPEED_MAX 4
+
+// Volume is stored from 0 to 5 but is an increment of 20 so 0 to 100 will be displayed
+#define VOLUME_OPTION_MIN       0
+#define VOLUME_OPTION_MAX       5
+#define VOLUME_OPTION_INCREMENT 20
+
+#define DEFAULT_GAME_SPEED    1
+#define DEFAULT_HIGH_CONTRAST false
+#define DEFAULT_MUSIC_VOLUME  VOLUME_OPTION_MAX
+#define DEFAULT_SOUND_VOLUME  VOLUME_OPTION_MAX
+
 /**
  * @brief A central location for all game variables.
  *
@@ -16,8 +29,26 @@
  */
 typedef struct
 {
-    s32 timer;
+    // Internal variables
+
+    s32 timer; // This might already exist in libtonc but idk so i'm just making my own
     u32 rng_seed;
+    u32 rng_step; // Position in the rng sequence.
+
+    // Variables visible by the player
+
+    int round;
+    int ante;
+    int money;
+
+    // Options variables
+
+    // BY DEFAULT IS SET TO 1, but if changed to 2 or more, should speed up all (or most) of the
+    // game aspects that should be sped up by speed, as in the original game.
+    u8 game_speed;
+    bool high_contrast;
+    u8 music_volume;
+    u8 sound_volume;
 } GameVariables;
 
 extern GameVariables g_game_vars;

include/save.h

@@ -0,0 +1,25 @@
+/**
+ * @file save.h
+ *
+ * @brief Utils functions to save/load data structures from/to the SRAM.
+ */
+#ifndef SAVE_H
+#define SAVE_H
+
+#include "game_variables.h"
+
+#include <tonc.h>
+
+/**
+ * @brief Save game data to SRAM.
+ */
+void save_game();
+
+/**
+ * @brief Load game data from SRAM.
+ *
+ * @sa save_game
+ */
+void load_game();
+
+#endif // SAVE_H

include/timer.h

@@ -9,4 +9,4 @@
 
 #define TM_ZERO 0
 
-#endif // TIMER_H
+#endif // TIMER_H

include/version.h

@@ -0,0 +1,11 @@
+/**
+ * @file version.h
+ *
+ * @brief Game ROM version global var declaration.
+ */
+#ifndef VERSION_H
+#define VERSION_H
+
+extern const char gbalatro_version[];
+
+#endif // VERSION_H

scripts/get_hash.py

@@ -20,7 +20,7 @@ if __name__ == "__main__":
         sys.exit(1)
 
     file_path = sys.argv[1]
-    pattern   = "GBALATRO_VERSION"
+    pattern   = "GBALATRO[_,-]VERSION"
 
     for offset, text in grep_binary_offsets(file_path, pattern):
         version = text.split(":")[1]

source/affine_background.c

@@ -13,7 +13,7 @@ static IWRAM_CODE void s_affine_background_prep_bgaff_arr();
 
 static BG_AFFINE _bgaff_arr[SCREEN_HEIGHT + 1];
 static AFF_SRC_EX _asx = {0};
-static enum AffineBackgroundID _background = AFFINE_BG_MAIN_MENU;
+static enum AffineBackgroundID _background = AFFINE_BG_NONE;
 static uint _timer = 0;
 
 void affine_background_init()
@@ -78,6 +78,11 @@ void affine_background_load_palette(const u16* src)
 
 void affine_background_change_background(enum AffineBackgroundID new_bg)
 {
+    if (_background == new_bg)
+    {
+        return;
+    }
+
     _background = new_bg;
 
     switch (_background)
@@ -110,6 +115,8 @@ void affine_background_change_background(enum AffineBackgroundID new_bg)
             GRIT_CPY(&se_mem[AFFINE_BG_SBB], affine_background_gfxMap);
             affine_background_load_palette(affine_background_gfxPal);
             break;
+        default:
+            break;
     }
 }
 

source/audio_utils.c

@@ -1,5 +1,7 @@
 #include "audio_utils.h"
 
+#include "game_variables.h"
+
 #include <maxmod.h>
 
 void play_sfx(mm_word id, mm_word rate, mm_byte volume)
@@ -8,7 +10,7 @@ void play_sfx(mm_word id, mm_word rate, mm_byte volume)
         {id},
         rate,
         0,
-        volume,
+        (volume * g_game_vars.sound_volume) / VOLUME_OPTION_MAX,
         SFX_DEFAULT_PAN,
     };
     mmEffectEx(&sfx);

source/blind.c

@@ -127,7 +127,7 @@ enum BlindType roll_blind_type(bool showdown)
     }
 
     // roll a random blind among the unbeaten ones
-    int random_blind_idx = rand() % list_get_len(p_unbeaten_blinds);
+    int random_blind_idx = get_rand() % list_get_len(p_unbeaten_blinds);
     Blind* random_blind = list_get_at_idx(p_unbeaten_blinds, random_blind_idx);
 
     return random_blind->type;

source/card.c

@@ -2,6 +2,7 @@
 
 #include "deck_gfx.h"
 #include "graphic_utils.h"
+#include "high_contrast_deck_pal_gfx.h"
 
 #include <maxmod.h>
 #include <stdlib.h>
@@ -21,7 +22,19 @@ const static u16 _card_sprite_lut[NUM_SUITS][NUM_RANKS] = {
 
 void card_init()
 {
-    GRIT_CPY(&pal_obj_mem[CARD_PB], deck_gfxPal);
+    toggle_high_contrast_cards(false);
+}
+
+void toggle_high_contrast_cards(bool enable)
+{
+    if (enable)
+    {
+        GRIT_CPY(&pal_obj_mem[CARD_PB], high_contrast_deck_pal_gfxPal);
+    }
+    else
+    {
+        GRIT_CPY(&pal_obj_mem[CARD_PB], deck_gfxPal);
+    }
 }
 
 // Card methods

source/game.c

@@ -8,16 +8,17 @@
 #include "background_main_menu_gfx.h"
 #include "background_shop_gfx.h"
 #include "bitset.h"
-#include "blind.h"
 #include "button.h"
 #include "card.h"
 #include "game/common_ui.h"
 #include "game/main_menu.h"
+#include "game/options_menu.h"
 #include "game_variables.h"
 #include "graphic_utils.h"
 #include "hand_analysis.h"
 #include "joker.h"
 #include "list.h"
+#include "save.h"
 #include "selection_grid.h"
 #include "soundbank.h"
 #include "splash_screen.h"
@@ -64,6 +65,7 @@
 #define CARD_UNFOCUSED_SEL_Y 15
 #define CARD_FOCUSED_SEL_Y   20
 
+// Timer defs
 #define TM_RESET_STATIC_VARS            30
 #define TM_END_POP_MENU_ANIM            13
 #define TM_START_ROUND_END_REWARDS_ANIM 1
@@ -87,6 +89,7 @@
 
 // TODO: Rename "PID" to "PAL_IDX"
 // Palette IDs
+
 #define BOSS_BLIND_PRIMARY_PID               1
 #define REROLL_BTN_PID                       3
 #define BLIND_SKIP_BTN_PID                   5
@@ -428,9 +431,6 @@ static const BG_POINT HAND_PLAY_POS         = {120,     70};
 
 typedef void (*SubStateActionFn)(void);
 
-// BY DEFAULT IS SET TO 1, but if changed to 2 or more, should speed up all (or most) of the game
-// aspects that should be sped up by speed, as in the original game.
-static int game_speed = 1;
 static enum BackgroundId background = BG_NONE;
 
 static StateInfo state_info[] = {
@@ -552,6 +552,18 @@ static enum PlayState play_state = PLAY_STARTING;
 static enum HandType hand_type = NONE;
 static ContainedHandTypes _contained_hands = {0};
 
+// Initialization of the global var
+// clang-format off
+GameVariables g_game_vars = {
+    0, 0, 0,
+    0, 0, 0,
+    DEFAULT_GAME_SPEED,
+    DEFAULT_HIGH_CONTRAST,
+    DEFAULT_MUSIC_VOLUME,
+    DEFAULT_SOUND_VOLUME
+};
+// clang-format on
+
 // The sprite that displays the blind when in "GAME_PLAYING/GAME_ROUND_END" state
 static Sprite* playing_blind_token = NULL;
 
@@ -586,9 +598,6 @@ static int max_discards = 4;
 static int hands = 0;
 static int discards = 0;
 
-static int round = 0;
-static int ante = 0;
-static int money = 0;
 static u32 score = 0;
 static u32 temp_score = 0; // This is the score that shows in the same spot as the hand type.
 static bool score_flames_active = false;
@@ -645,9 +654,6 @@ static int shortcut_joker_count = 0;
 
 static int four_fingers_joker_count = 0;
 
-GBAL_UNUSED
-GameVariables g_game_vars;
-
 GBAL_UNUSED
 static inline bool is_shop_joker_avail(int joker_id)
 {
@@ -729,7 +735,7 @@ static inline void jokers_available_to_shop_init(void)
 static void reroll_boss_blind(bool no_tiles)
 {
     // Showdown blinds only show up on ante 8, 16, etc...
-    next_boss_blind = roll_blind_type((ante % 8 == 0) && (ante > 0));
+    next_boss_blind = roll_blind_type((g_game_vars.ante % 8 == 0) && (g_game_vars.ante > 0));
     if (!no_tiles)
     {
         apply_blind_tiles(next_boss_blind, BOSS_BLIND_TOKEN_LAYER);
@@ -781,6 +787,8 @@ void game_init()
 
     jokers_available_to_shop_init();
 
+    load_game();
+
     hands = max_hands;
     discards = max_discards;
     g_game_vars.timer = TM_ZERO;
@@ -788,10 +796,10 @@ void game_init()
     blinds_states[0] = BLIND_STATE_CURRENT;
     blinds_states[1] = BLIND_STATE_UPCOMING;
     blinds_states[2] = BLIND_STATE_UPCOMING;
-    ante = STARTING_ANTE;
-    money = STARTING_MONEY;
+    g_game_vars.ante = STARTING_ANTE;
+    g_game_vars.money = STARTING_MONEY;
     score = STARTING_SCORE;
-    round = 0;
+    g_game_vars.round = 0;
 
     // Initialize/reset unbeaten Boss/Showdown Blinds so they are all available
     init_unbeaten_blinds_list(false);
@@ -918,6 +926,12 @@ void game_change_state(enum GameState new_game_state)
     }
 }
 
+u32 get_rand()
+{
+    g_game_vars.rng_step++;
+    return rand();
+}
+
 CardObject** get_hand_array(void)
 {
     return hand;
@@ -1037,15 +1051,14 @@ int get_num_hands_remaining(void)
     return hands;
 }
 
-int get_game_speed(void)
+enum BlindType get_current_blind()
 {
-    return game_speed;
+    return current_blind;
 }
 
-// for the future when a menu actually lets this variable be changed.
-void set_game_speed(int new_game_speed)
+enum BlindType get_next_boss_blind()
 {
-    game_speed = new_game_speed;
+    return next_boss_blind;
 }
 
 u32 get_chips(void)
@@ -1068,16 +1081,6 @@ void set_mult(u32 new_mult)
     mult = new_mult;
 }
 
-int get_money(void)
-{
-    return money;
-}
-
-void set_money(int new_money)
-{
-    money = new_money;
-}
-
 void set_retrigger(bool new_retrigger)
 {
     retrigger = new_retrigger;
@@ -1089,7 +1092,7 @@ void display_money()
     tte_erase_rect_wrapper(MONEY_TEXT_RECT);
 
     char money_str_buff[INT_MAX_DIGITS + 2]; // + 2 for null terminator and "$" sign
-    snprintf(money_str_buff, sizeof(money_str_buff), "$%d", money);
+    snprintf(money_str_buff, sizeof(money_str_buff), "$%d", g_game_vars.money);
 
     // Bias left so the number is centered and the "$" sign is on the left
     update_text_rect_to_center_str(&money_text_rect, money_str_buff, SCREEN_LEFT);
@@ -1806,7 +1809,7 @@ static void display_score(u32 value)
 static void check_flaming_score(void)
 {
     u32 curr_score = u32_protected_mult(chips, mult);
-    u32 required_score = blind_get_requirement(current_blind, ante);
+    u32 required_score = blind_get_requirement(current_blind, g_game_vars.ante);
     if (curr_score >= required_score && !score_flames_active)
     {
         // start flaming score
@@ -1834,7 +1837,7 @@ static void display_round(void)
         ROUND_TEXT_RECT.left,
         ROUND_TEXT_RECT.top,
         TTE_YELLOW_PB,
-        round
+        g_game_vars.round
     );
 }
 
@@ -1935,14 +1938,14 @@ static inline void deck_shuffle(void)
 {
     for (int i = deck_top; i > 0; i--)
     {
-        int j = rand() % (i + 1);
+        int j = get_rand() % (i + 1);
         Card* temp = deck[i];
         deck[i] = deck[j];
         deck[j] = temp;
     }
 }
 
-static void game_round_on_init()
+static void game_round_on_init(void)
 {
     hand_state = HAND_DRAW;
     cards_drawn = 0;
@@ -1974,7 +1977,7 @@ static void game_round_on_init()
     }
 
     Rect blind_req_text_rect = BLIND_REQ_TEXT_RECT;
-    u32 blind_requirement = blind_get_requirement(current_blind, ante);
+    u32 blind_requirement = blind_get_requirement(current_blind, g_game_vars.ante);
 
     char blind_req_str_buff[UINT_MAX_DIGITS + 1];
 
@@ -2019,14 +2022,14 @@ static void game_over_init(void)
     main_bg_se_copy_rect(NEW_RUN_BTN_SRC_RECT, NEW_RUN_BTN_DEST_POS);
 }
 
-static void game_lose_on_init()
+static void game_lose_on_init(void)
 {
     game_over_init();
     // Using the text color to match the "Game Over" text
     affine_background_set_color(TEXT_CLR_RED);
 }
 
-static void game_win_on_init()
+static void game_win_on_init(void)
 {
     game_over_init();
     // Using the text color to match the "You Win" text
@@ -2036,8 +2039,9 @@ static void game_win_on_init()
 // General functions
 static inline void set_seed(int seed)
 {
+    srand(seed);
     g_game_vars.rng_seed = seed;
-    srand(g_game_vars.rng_seed);
+    g_game_vars.rng_step = 0;
 }
 
 // Playing state functions
@@ -2195,7 +2199,7 @@ static bool game_playing_hand_row_on_selection_changed(
              */
             play_sfx(
                 SFX_CARD_FOCUS,
-                MM_BASE_PITCH_RATE + rand() % CARD_FOCUS_SFX_PITCH_OFFSET_RANGE,
+                MM_BASE_PITCH_RATE + get_rand() % CARD_FOCUS_SFX_PITCH_OFFSET_RANGE,
                 SFX_DEFAULT_VOLUME
             );
         }
@@ -2215,7 +2219,7 @@ static bool game_playing_hand_row_on_selection_changed(
              */
             play_sfx(
                 SFX_CARD_FOCUS,
-                MM_BASE_PITCH_RATE + rand() % CARD_FOCUS_SFX_PITCH_OFFSET_RANGE,
+                MM_BASE_PITCH_RATE + get_rand() % CARD_FOCUS_SFX_PITCH_OFFSET_RANGE,
                 SFX_DEFAULT_VOLUME
             );
         }
@@ -2377,13 +2381,13 @@ static inline void game_playing_handle_round_over(void)
 {
     enum GameState next_state = GAME_STATE_ROUND_END;
 
-    if (score >= blind_get_requirement(current_blind, ante))
+    if (score >= blind_get_requirement(current_blind, g_game_vars.ante))
     {
         if (current_blind > BLIND_TYPE_BIG)
         {
-            if (ante < MAX_ANTE)
+            if (g_game_vars.ante < MAX_ANTE)
             {
-                display_ante(++ante);
+                display_ante(++g_game_vars.ante);
 
                 // mark current boss blind as beaten and allow for reroll
                 set_blind_beaten(next_boss_blind);
@@ -2706,7 +2710,7 @@ static bool check_and_score_joker_for_event(
 
 static inline bool game_round_is_over(void)
 {
-    return hands == 0 || score >= blind_get_requirement(current_blind, ante);
+    return hands == 0 || score >= blind_get_requirement(current_blind, g_game_vars.ante);
 }
 
 // Basically a copy of HAND_DISCARD
@@ -3156,7 +3160,7 @@ static inline void game_playing_process_input_and_state(void)
             display_chips();
 
             static const int SCORE_CALC_SFX_PITCH_SHIFT = -102; // -10% OF MM_BASE_PITCH_RATE
-            static const int SCORE_CALC_SFX_VOLUME = 204;       // 80% MM_FULL_VOLUME
+            static const int SCORE_CALC_SFX_VOLUME = 204;       // 80% MM_SFX_FULL_VOLUME
 
             // The chips calculation SFX is the same as button
             play_sfx(
@@ -3171,10 +3175,10 @@ static inline void game_playing_process_input_and_state(void)
         /* Using fixed point in case the score is lower than NUM_SCORE_LERP_STEPS and then
          * then the division rounds it down to 0 and it's never added to the total.
          * The operation is equivalent to
-         * fxdiv(int2fx(temp_score * get_game_speed()), int2fx(NUM_SCORE_LERP_STEPS))
+         * fxdiv(int2fx(temp_score * g_game_vars.game_speed), int2fx(NUM_SCORE_LERP_STEPS))
          */
-        lerped_temp_score -= int2fx(temp_score * get_game_speed()) / NUM_SCORE_LERP_STEPS;
-        lerped_score += int2fx(temp_score * get_game_speed()) / NUM_SCORE_LERP_STEPS;
+        lerped_temp_score -= int2fx(temp_score * g_game_vars.game_speed) / NUM_SCORE_LERP_STEPS;
+        lerped_score += int2fx(temp_score * g_game_vars.game_speed) / NUM_SCORE_LERP_STEPS;
 
         if (lerped_temp_score > 0)
         {
@@ -3504,7 +3508,7 @@ static inline void game_playing_process_flaming_score(void)
     }
 }
 
-static void game_playing_on_update()
+static void game_playing_on_update(void)
 {
     // Background logic (thissss might be moved to the card'ssss logic later. I'm a sssssnake)
     if (hand_state == HAND_DRAW || hand_state == HAND_DISCARD || hand_state == HAND_SELECT)
@@ -3537,13 +3541,13 @@ static void game_playing_on_update()
 
 static int calculate_interest_reward(void)
 {
-    int reward = (money / 5) * INTEREST_PER_5;
+    int reward = (g_game_vars.money / 5) * INTEREST_PER_5;
     if (reward > MAX_INTEREST)
         reward = MAX_INTEREST;
     return reward;
 }
 
-static void game_round_end_on_exit()
+static void game_round_end_on_exit(void)
 {
     // Cleanup blind tokens from this round to avoid accumulating
     // allocated blind sprites each round
@@ -3555,7 +3559,7 @@ static void game_round_end_on_exit()
     // TODO: Reuse sprites for blind selection?
 }
 
-static void game_round_end_on_update()
+static void game_round_end_on_update(void)
 {
     if (state_info[game_state].substate == ROUND_END_EXIT)
     {
@@ -3606,7 +3610,7 @@ static void game_round_end_display_finished_blind()
 {
     obj_unhide(round_end_blind_token->obj, 0);
 
-    int current_ante = ante;
+    int current_ante = g_game_vars.ante;
 
     // Beating the boss blind increases the ante, so we need to display the previous ante value
     if (current_blind > BLIND_TYPE_BIG)
@@ -3854,7 +3858,7 @@ static void game_round_end_display_rewards()
 static inline void game_round_end_cashout(void)
 {
     // Reward the player
-    money += hands + blind_get_reward(current_blind) + calculate_interest_reward();
+    g_game_vars.money += hands + blind_get_reward(current_blind) + calculate_interest_reward();
     display_money();
 
     hands = max_hands;          // Reset the hands to the maximum
@@ -3969,7 +3973,7 @@ static inline int game_shop_get_rand_available_joker_id(void)
         return UNDEFINED;
 
     int matching_joker_ids[jokers_avail_size];
-    int fallback_random_idx = random() % jokers_avail_size;
+    int fallback_random_idx = get_rand() % jokers_avail_size;
     int fallback_random_joker_id = UNDEFINED;
     int match_count = 0;
 
@@ -3989,7 +3993,7 @@ static inline int game_shop_get_rand_available_joker_id(void)
     }
 
     int selected_joker_id =
-        (match_count > 0) ? matching_joker_ids[random() % match_count] : fallback_random_joker_id;
+        (match_count > 0) ? matching_joker_ids[get_rand() % match_count] : fallback_random_joker_id;
 
     return selected_joker_id;
 }
@@ -4160,7 +4164,7 @@ static inline void game_sell_joker(int joker_idx)
         return;
 
     JokerObject* joker_object = (JokerObject*)list_get_at_idx(&_owned_jokers_list, joker_idx);
-    money += joker_get_sell_value(joker_object->joker);
+    g_game_vars.money += joker_get_sell_value(joker_object->joker);
     display_money();
     erase_price_under_sprite_object(joker_object->sprite_object);
 
@@ -4216,8 +4220,8 @@ static inline void game_shop_buy_joker(int shop_joker_idx)
 {
     JokerObject* joker_object = (JokerObject*)list_get_at_idx(&_shop_jokers_list, shop_joker_idx);
 
-    money -= joker_object->joker->value; // Deduct the money spent on the joker
-    display_money();                     // Update the money display
+    g_game_vars.money -= joker_object->joker->value; // Deduct the money spent on the joker
+    display_money();                                 // Update the money display
     erase_price_under_sprite_object(joker_object->sprite_object);
     sprite_object_set_focus(joker_object->sprite_object, false);
     add_to_held_jokers(joker_object);
@@ -4255,7 +4259,7 @@ static void shop_top_row_on_key_transit(SelectionGrid* selection_grid, Selection
         JokerObject* joker_object =
             (JokerObject*)list_get_at_idx(&_shop_jokers_list, shop_joker_idx);
         if (joker_object == NULL || list_get_len(&_owned_jokers_list) >= MAX_JOKERS_HELD_SIZE ||
-            money < joker_object->joker->value)
+            g_game_vars.money < joker_object->joker->value)
         {
             return;
         }
@@ -4354,7 +4358,7 @@ static bool shop_reroll_row_on_selection_changed(
 
 static inline void game_shop_reroll(int* reroll_cost)
 {
-    money -= *reroll_cost;
+    g_game_vars.money -= *reroll_cost;
     display_money(); // Update the money display
 
     ListItr itr = list_itr_create(&_shop_jokers_list);
@@ -4405,7 +4409,7 @@ static void shop_reroll_row_on_key_transit(SelectionGrid* selection_grid, Select
         return;
     }
 
-    if (money >= reroll_cost)
+    if (g_game_vars.money >= reroll_cost)
     {
         // TODO: Add money sound effect
         play_sfx(SFX_BUTTON, MM_BASE_PITCH_RATE, BUTTON_SFX_VOLUME);
@@ -4503,7 +4507,7 @@ static inline void game_shop_lights_anim_frame(void)
     memcpy16(&pal_bg_mem[SHOP_LIGHTS_1_PID], &shifted_palette[3], 1);
 }
 
-static void game_shop_on_update()
+static void game_shop_on_update(void)
 {
     change_background(BG_SHOP);
 
@@ -4536,7 +4540,7 @@ static void game_shop_on_update()
     shop_state_actions[substate]();
 }
 
-static void game_shop_on_exit()
+static void game_shop_on_exit(void)
 {
     ListItr itr = list_itr_create(&_shop_jokers_list);
     JokerObject* joker_object;
@@ -4554,9 +4558,11 @@ static void game_shop_on_exit()
     list_clear(&_shop_jokers_list);
 
     increment_blind(BLIND_STATE_DEFEATED); // TODO: Move to game_round_end()?
+
+    save_game();
 }
 
-static void game_blind_select_on_init()
+static void game_blind_select_on_init(void)
 {
     change_background(BG_BLIND_SELECT);
     selection_x = 0;
@@ -4565,7 +4571,7 @@ static void game_blind_select_on_init()
     play_sfx(SFX_POP, MM_BASE_PITCH_RATE, SFX_DEFAULT_VOLUME);
 }
 
-static void game_blind_select_on_update()
+static void game_blind_select_on_update(void)
 {
     if (state_info[game_state].substate == BLIND_SELECT_MAX)
     {
@@ -4638,7 +4644,7 @@ static inline void game_blind_select_print_blind_req(enum BlindTokens blind)
 {
     Rect blind_req_score_rect = game_blind_select_get_req_score_rect(blind);
 
-    u32 blind_req = blind_get_requirement(get_blind_type_from_token(blind), ante);
+    u32 blind_req = blind_get_requirement(get_blind_type_from_token(blind), g_game_vars.ante);
 
     char blind_req_str_buff[UINT_MAX_DIGITS + 1];
     truncate_uint_to_suffixed_str(
@@ -4736,7 +4742,7 @@ static void game_blind_select_handle_input()
             play_sfx(SFX_BUTTON, MM_BASE_PITCH_RATE, BUTTON_SFX_VOLUME);
             state_info[game_state].substate = BLIND_SELECTED_ANIM_SEQ;
             g_game_vars.timer = TM_ZERO;
-            ++round;
+            ++g_game_vars.round;
             display_round();
         }
         else if (current_blind <= BLIND_TYPE_BIG)
@@ -4853,25 +4859,25 @@ static void game_blind_select_display_blind_panel()
     }
 }
 
-static void game_blind_select_on_exit()
+static void game_blind_select_on_exit(void)
 {
     selection_y = 0;
     background = UNDEFINED;
 }
 
-void game_start()
+void game_start(void)
 {
-    set_seed(g_game_vars.rng_seed);
     // set_seed(9); // 9 is a full house
+    set_seed(g_game_vars.rng_seed);
 
     affine_background_change_background(AFFINE_BG_GAME);
 
-    // Normally I would just cache these and hide/unhide but I didn't feel like dealing with
-    // defining a layer for it
-
     hands = max_hands;
     discards = max_discards;
 
+    // Activate high contrast palette for cards if loaded settings tell us to
+    toggle_high_contrast_cards(g_game_vars.high_contrast);
+
     // Fill the deck with all the cards. Later on this can be replaced with a more dynamic system
     // that allows for different decks and card types.
     for (int suit = 0; suit < NUM_SUITS; suit++)
@@ -4912,7 +4918,7 @@ void game_start()
         ANTE_TEXT_RECT.left,
         ANTE_TEXT_RECT.top,
         TTE_YELLOW_PB,
-        ante,
+        g_game_vars.ante,
         TTE_WHITE_PB,
         MAX_ANTE
     ); // Ante
@@ -4934,7 +4940,7 @@ static inline void game_over_process_user_input()
     }
 }
 
-static void game_lose_on_update()
+static void game_lose_on_update(void)
 {
     if (g_game_vars.timer < GAME_OVER_ANIM_FRAMES)
     {
@@ -4956,7 +4962,7 @@ static void game_lose_on_update()
 // This function isn't set in stone. This is just a placeholder
 // allowing the player to restart the game. Thought it would be nice to have
 // util we decide what we want to do after a game over.
-static void game_over_on_exit()
+static void game_over_on_exit(void)
 {
     while (list_get_len(&_owned_jokers_list) > 0)
     {
@@ -4996,7 +5002,7 @@ static void game_over_on_exit()
         ANTE_TEXT_RECT.left,
         ANTE_TEXT_RECT.top,
         TTE_YELLOW_PB,
-        ante,
+        g_game_vars.ante,
         TTE_WHITE_PB,
         MAX_ANTE
     );
@@ -5004,7 +5010,7 @@ static void game_over_on_exit()
     affine_background_load_palette(affine_background_gfxPal);
 }
 
-static void game_win_on_update()
+static void game_win_on_update(void)
 {
     if (g_game_vars.timer < GAME_OVER_ANIM_FRAMES)
     {

source/game/common_ui.c

@@ -2,6 +2,7 @@
 
 #include "game.h"
 #include "game/main_menu.h"
+#include "game/options_menu.h"
 
 typedef void (*BackgroundRenderCallback)(void);
 
@@ -15,18 +16,18 @@ static const BackgroundRenderCallback bgCallbacks[] = {
     [BG_ROUND_END] = NULL,
     [BG_SHOP] = NULL,
     [BG_BLIND_SELECT] = NULL,
+    [BG_OPTIONS_MENU] = game_options_menu_change_background,
     [BG_MAIN_MENU] = game_main_menu_change_background,
 };
 
 void change_background(enum BackgroundId id)
 {
-    if (id == BG_MAIN_MENU)
+    if (id != background && bgCallbacks[id] != NULL)
     {
-        if (id != background)
-        {
-            bgCallbacks[id]();
-        }
+        bgCallbacks[id]();
     }
-    change_background_legacy(id);
     background = id;
+
+    // Can be removed once all states have their own "change_background" func
+    change_background_legacy(id);
 }

source/game/main_menu.c

@@ -9,29 +9,79 @@
 #include "game/common_ui.h"
 #include "game_variables.h"
 #include "graphic_utils.h"
+#include "selection_grid.h"
 #include "soundbank.h"
 #include "sprite.h"
+#include "version.h"
 
 #include <stdint.h>
 #include <tonc.h>
 #include <tonc_math.h>
 #include <tonc_memdef.h>
 
-static const u32 PLAY_BUTTON_OUTLINE_PID = 2;
-static const u32 PLAY_BUTTON_MAIN_COLOR_PID = 5;
+#define PLAY_BUTTON_MAIN_COLOR_PID    5
+#define PLAY_BUTTON_OUTLINE_PID       6
+#define OPTIONS_BUTTON_MAIN_COLOR_PID 7
+#define OPTIONS_BUTTON_OUTLINE_PID    1
 
-static const u32 IMPLEMENTED_BUTTONS = 1; // Remove this once all buttons are implemented
-static const u32 PLAY_BTN_IDX = 0;
+enum MainButtons
+{
+    PLAY_BTN_IDX,
+    OPTIONS_BTN_IDX,
+    MAIN_MENU_NB_BTN
+};
 
 // Pixel sizes
 #define MAIN_MENU_ACE_T_X 88
 #define MAIN_MENU_ACE_T_Y 26
 
+// clang-format off
+static const BG_POINT GBALATRO_VERSION_TEXT_POS  = {0, 152};
+static const Rect     GBALATRO_VERSION_TEXT_RECT = {0, 152, 240, 160};
+// clang-format on
+
+// Define SelectionGrid for the main menu buttons
+
+static int main_menu_return_row_size(void);
+static bool main_menu_on_selection_changed(
+    SelectionGrid* selection_grid,
+    int row_idx,
+    const Selection* prev_selection,
+    const Selection* new_selection
+);
+static void main_menu_on_key_transit(SelectionGrid* selection_grid, Selection* selection);
+
+static void play_on_pressed(void);
+static void options_on_pressed(void);
+
+// clang-format off
+static SelectionGridRow main_menu_selection_rows[] = {
+    {
+        0,
+        main_menu_return_row_size,
+        main_menu_on_selection_changed,
+        main_menu_on_key_transit,
+        {.wrap = false}
+    },
+};
+
+static Button main_menu_buttons[] = {
+    {PLAY_BUTTON_OUTLINE_PID,    PLAY_BUTTON_MAIN_COLOR_PID,    play_on_pressed,    NULL},
+    {OPTIONS_BUTTON_OUTLINE_PID, OPTIONS_BUTTON_MAIN_COLOR_PID, options_on_pressed, NULL},
+};
+
+static SelectionGrid main_menu_selection_grid = {
+    main_menu_selection_rows,
+    1,
+    {0, 0}
+};
+// clang-format on
+
 // Main menu sprite - the ace of spades
 static CardObject* main_menu_ace = NULL;
 
-// Current selected button index
-static int selection_x = 0;
+// Keep track of last highlighted button
+static enum MainButtons last_highlighted_button = PLAY_BTN_IDX;
 
 void game_main_menu_change_background(void)
 {
@@ -42,11 +92,14 @@ void game_main_menu_change_background(void)
     GRIT_CPY(&tile_mem[MAIN_BG_CBB], background_main_menu_gfxTiles);
     GRIT_CPY(&se_mem[MAIN_BG_SBB], background_main_menu_gfxMap);
 
-    // Disable the button highlight colors
-    memcpy16(&pal_bg_mem[PLAY_BUTTON_OUTLINE_PID], &pal_bg_mem[PLAY_BUTTON_MAIN_COLOR_PID], 1);
+    // Disable all button highlight colors
+    for (int i = 0; i < MAIN_MENU_NB_BTN; i++)
+    {
+        button_set_highlight(&main_menu_buttons[i], false);
+    }
 }
 
-void game_main_menu_on_init()
+void game_main_menu_on_init(void)
 {
     affine_background_change_background(AFFINE_BG_MAIN_MENU);
     change_background(BG_MAIN_MENU);
@@ -58,10 +111,18 @@ void game_main_menu_on_init()
     main_menu_ace->sprite_object->ty = int2fx(MAIN_MENU_ACE_T_Y);
     main_menu_ace->sprite_object->y = main_menu_ace->sprite_object->ty;
     main_menu_ace->sprite_object->tscale = float2fx(0.8f);
-    selection_x = 0;
+    card_object_update(main_menu_ace);
+
+    // Select last highlighted button, Play button by default.
+    // e.g. if we return from the options menu, we want the Options button to be highlighted.
+    Selection sel_init = {last_highlighted_button, 0};
+    main_menu_selection_grid.selection = sel_init;
+
+    // Highlight current button
+    button_set_highlight(&main_menu_buttons[main_menu_selection_grid.selection.x], true);
 }
 
-void game_main_menu_on_update()
+void game_main_menu_on_update(void)
 {
     card_object_update(main_menu_ace);
     main_menu_ace->sprite_object->trotation = lu_sin((g_game_vars.timer << 8) / 2) / 3;
@@ -75,41 +136,91 @@ void game_main_menu_on_update()
         g_game_vars.rng_seed *= 2;
     }
 
-    if (key_hit(KEY_LEFT))
-    {
-        if (selection_x > 0)
-        {
-            selection_x--;
-        }
-    }
-    else if (key_hit(KEY_RIGHT))
-    {
-        if (selection_x < IMPLEMENTED_BUTTONS - 1)
-        {
-            selection_x++;
-        }
-    }
-
-    if (selection_x == PLAY_BTN_IDX)
-    {
-        memset16(&pal_bg_mem[PLAY_BUTTON_OUTLINE_PID], BTN_HIGHLIGHT_COLOR, 1);
-
-        if (key_hit(SELECT_CARD))
-        {
-            play_sfx(SFX_BUTTON, MM_BASE_PITCH_RATE, BUTTON_SFX_VOLUME);
-            game_change_state(GAME_STATE_GAME_START);
-        }
-    }
-    else
-    {
-        memcpy16(&pal_bg_mem[PLAY_BUTTON_OUTLINE_PID], &pal_bg_mem[PLAY_BUTTON_MAIN_COLOR_PID], 1);
-    }
+    selection_grid_process_input(&main_menu_selection_grid);
 }
 
-void game_main_menu_on_exit()
+void game_main_menu_on_exit(void)
 {
+    // Save selected button
+    last_highlighted_button = main_menu_selection_grid.selection.x;
+
     // Normally I would just cache these and hide/unhide but I didn't feel like dealing with
     // defining a layer for it
     card_destroy(&main_menu_ace->card);
     card_object_destroy(&main_menu_ace);
 }
+
+// Implement SelectionGrid handler functions
+
+static int main_menu_return_row_size(void)
+{
+    return MAIN_MENU_NB_BTN;
+}
+
+static bool main_menu_on_selection_changed(
+    SelectionGrid* selection_grid,
+    int row_idx,
+    const Selection* prev_selection,
+    const Selection* new_selection
+)
+{
+    if (prev_selection->x >= 0 && prev_selection->x < MAIN_MENU_NB_BTN)
+    {
+        button_set_highlight(&main_menu_buttons[prev_selection->x], false);
+    }
+
+    play_sfx(SFX_BUTTON, MM_BASE_PITCH_RATE, BUTTON_SFX_VOLUME);
+    button_set_highlight(&main_menu_buttons[new_selection->x], true);
+
+    return true;
+}
+
+static void main_menu_on_key_transit(SelectionGrid* selection_grid, Selection* selection)
+{
+    // DEBUG: toggle git hash display by pressing L+R+START+SELECT
+    static bool combo_pressed = false;
+    static bool show_version = false;
+    if (key_is_down(KEY_START) && key_is_down(KEY_SELECT) && key_is_down(KEY_L) &&
+        key_is_down(KEY_R))
+    {
+        if (!combo_pressed)
+        {
+            show_version = !show_version;
+            if (show_version)
+            {
+                tte_printf(
+                    "#{P:%d,%d; cx:0x%X000}%s",
+                    GBALATRO_VERSION_TEXT_POS.x,
+                    GBALATRO_VERSION_TEXT_POS.y,
+                    TTE_WHITE_PB,
+                    gbalatro_version
+                );
+            }
+            else
+            {
+                tte_erase_rect_wrapper(GBALATRO_VERSION_TEXT_RECT);
+            }
+        }
+
+        combo_pressed = true;
+    }
+    else
+    {
+        combo_pressed = false;
+    }
+
+    if (key_hit(SELECT_CARD))
+    {
+        button_press(&main_menu_buttons[selection->x]);
+    }
+}
+
+static void play_on_pressed(void)
+{
+    game_change_state(GAME_STATE_GAME_START);
+}
+
+static void options_on_pressed(void)
+{
+    game_change_state(GAME_STATE_OPTIONS_MENU);
+}

source/game/options_menu.c

@@ -0,0 +1,624 @@
+#include "game/options_menu.h"
+
+#include "affine_background.h"
+#include "audio_utils.h"
+#include "background_options_menu_gfx.h"
+#include "button.h"
+#include "game.h"
+#include "game/common_ui.h"
+#include "game_variables.h"
+#include "graphic_utils.h"
+#include "save.h"
+#include "selection_grid.h"
+#include "soundbank.h"
+#include "util.h"
+
+#include <stdint.h>
+#include <string.h>
+#include <tonc.h>
+#include <tonc_math.h>
+#include <tonc_memdef.h>
+
+// Button indices
+enum OptionButtons
+{
+    GAME_SPEED_BTN_IDX,
+    HIGH_CONTRAST_BTN_IDX,
+    MUSIC_VOLUME_BTN_IDX,
+    SOUND_VOLUME_BTN_IDX,
+    BACK_BTN_IDX,
+    NB_OPTIONS_BUTTONS
+};
+enum OptionSpeedButtons
+{
+    GAME_SPEED_DOWN_BTN_IDX,
+    GAME_SPEED_UP_BTN_IDX,
+    NB_GAME_SPEED_BUTTONS
+};
+
+// Color palette indices
+#define MENU_BUTTON_MAIN_COLOR_PAL_IDX          1
+#define BACK_BUTTON_MAIN_COLOR_PAL_IDX          3
+#define SPEED_DOWN_BUTTON_OUTLINE_COLOR_PAL_IDX 4
+#define SPEED_BUTTON_OUTLINE_COLOR_PAL_IDX      5
+#define SPEED_UP_BUTTON_OUTLINE_COLOR_PAL_IDX   6
+#define CONTRAST_BUTTON_OUTLINE_COLOR_PAL_IDX   7
+#define MUSIC_BUTTON_OUTLINE_COLOR_PAL_IDX      8
+#define SOUND_BUTTON_OUTLINE_COLOR_PAL_IDX      9
+#define BACK_BUTTON_OUTLINE_COLOR_PAL_IDX       10
+
+// Define selection grid for the menu buttons
+
+static void game_speed_down_on_pressed(void);
+static void game_speed_up_on_pressed(void);
+static void high_contrast_on_pressed(void);
+static void back_on_pressed(void);
+static int options_menu_return_row_size(void);
+static void options_menu_row_on_key_transit(SelectionGrid* selection_grid, Selection* selection);
+static bool game_speed_row_on_selection_changed(
+    SelectionGrid* selection_grid,
+    int row_idx,
+    const Selection* prev_selection,
+    const Selection* new_selection
+);
+static bool music_volume_row_on_selection_changed(
+    SelectionGrid* selection_grid,
+    int row_idx,
+    const Selection* prev_selection,
+    const Selection* new_selection
+);
+static bool sound_volume_row_on_selection_changed(
+    SelectionGrid* selection_grid,
+    int row_idx,
+    const Selection* prev_selection,
+    const Selection* new_selection
+);
+static bool regular_button_row_on_selection_changed(
+    SelectionGrid* selection_grid,
+    int row_idx,
+    const Selection* prev_selection,
+    const Selection* new_selection
+);
+
+// clang-format off
+static SelectionGridRow options_menu_selection_rows[] = {
+    {
+        GAME_SPEED_BTN_IDX,
+        options_menu_return_row_size,
+        game_speed_row_on_selection_changed,
+        NULL,
+        {.wrap = true} // The wrapping is used to allow button activation with Left/Right arrows by
+                       // putting logic into the `game_speed_row_on_selection_changed` function
+    },
+    {
+        HIGH_CONTRAST_BTN_IDX,
+        options_menu_return_row_size,
+        regular_button_row_on_selection_changed,
+        options_menu_row_on_key_transit,
+        {.wrap = false}
+    },
+    {
+        MUSIC_VOLUME_BTN_IDX,
+        options_menu_return_row_size,
+        music_volume_row_on_selection_changed,
+        NULL,
+        {.wrap = true} // Same trick as Game Speed button
+    },
+    {
+        SOUND_VOLUME_BTN_IDX,
+        options_menu_return_row_size,
+        sound_volume_row_on_selection_changed,
+        NULL,
+        {.wrap = true} // Same trick as Game Speed button
+    },
+    {
+        BACK_BTN_IDX,
+        options_menu_return_row_size,
+        regular_button_row_on_selection_changed,
+        options_menu_row_on_key_transit,
+        {.wrap = false}
+    }
+};
+
+static Button options_menu_buttons[] = {
+    {SPEED_BUTTON_OUTLINE_COLOR_PAL_IDX,    MENU_BUTTON_MAIN_COLOR_PAL_IDX, NULL,                     NULL},
+    {CONTRAST_BUTTON_OUTLINE_COLOR_PAL_IDX, MENU_BUTTON_MAIN_COLOR_PAL_IDX, high_contrast_on_pressed, NULL},
+    {MUSIC_BUTTON_OUTLINE_COLOR_PAL_IDX,    MENU_BUTTON_MAIN_COLOR_PAL_IDX, NULL,                     NULL},
+    {SOUND_BUTTON_OUTLINE_COLOR_PAL_IDX,    MENU_BUTTON_MAIN_COLOR_PAL_IDX, NULL,                     NULL},
+    {BACK_BUTTON_OUTLINE_COLOR_PAL_IDX,     BACK_BUTTON_MAIN_COLOR_PAL_IDX, back_on_pressed,          NULL}
+};
+
+static Button game_speed_buttons[] = {
+    {SPEED_DOWN_BUTTON_OUTLINE_COLOR_PAL_IDX, MENU_BUTTON_MAIN_COLOR_PAL_IDX, game_speed_down_on_pressed, NULL},
+    {SPEED_UP_BUTTON_OUTLINE_COLOR_PAL_IDX,   MENU_BUTTON_MAIN_COLOR_PAL_IDX, game_speed_up_on_pressed,   NULL},
+};
+// clang-format on
+
+const Selection OPTIONS_MENU_INIT_SEL = {0, 0};
+
+static SelectionGrid options_menu_selection_grid = {
+    options_menu_selection_rows,
+    NB_OPTIONS_BUTTONS,
+    OPTIONS_MENU_INIT_SEL
+};
+
+// Positions/Rects used to construct and update the menu
+// clang-format off
+
+// Values in tiles
+static const Rect     OPTIONS_SPEED_DOWN_ACTIVE_BTN_SRC_RECT   = { 3, 20,  3, 21};
+static const Rect     OPTIONS_SPEED_DOWN_DISABLED_BTN_SRC_RECT = { 9, 22,  9, 23};
+static const BG_POINT OPTIONS_SPEED_DOWN_BTN_DEST_POS          = {11,  3};
+static const Rect     OPTIONS_SPEED_UP_ACTIVE_BTN_SRC_RECT     = {10, 20, 10, 21};
+static const Rect     OPTIONS_SPEED_UP_DISABLED_BTN_SRC_RECT   = {10, 22, 10, 23};
+static const BG_POINT OPTIONS_SPEED_UP_BTN_DEST_POS            = {18,  3};
+static const Rect     OPTIONS_SPEED_VALUES[GAME_SPEED_MAX]   = { { 6, 20,  7, 21},
+                                                                 { 3, 22,  4, 23},
+                                                                 { 5, 22,  6, 23},
+                                                                 { 7, 22,  8, 23} };
+static const BG_POINT OPTIONS_SPEED_VALUE_DEST_POS             = {14,  3};
+
+static const Rect     OPTIONS_CONTRAST_VALUE_YES_SRC_RECT      = { 4, 24,  7, 25};
+static const Rect     OPTIONS_CONTRAST_VALUE_NO_SRC_RECT       = { 9, 24, 12, 25};
+static const BG_POINT OPTIONS_CONTRAST_VALUE_DEST_POS          = {13,  7};
+
+static const Rect     OPTIONS_MUSIC_SLIDER_FULL_SRC            = {12, 20, 12, 20};
+static const Rect     OPTIONS_MUSIC_SLIDER_MID_SRC             = {13, 20, 13, 20};
+static const Rect     OPTIONS_MUSIC_SLIDER_EMPTY_SRC           = {14, 20, 14, 20};
+static const Rect     OPTIONS_SOUND_SLIDER_FULL_SRC            = {12, 22, 12, 22};
+static const Rect     OPTIONS_SOUND_SLIDER_MID_SRC             = {13, 22, 13, 22};
+static const Rect     OPTIONS_SOUND_SLIDER_EMPTY_SRC           = {14, 22, 14, 22};
+static const BG_POINT OPTIONS_MUSIC_SLIDER_START_POS           = { 5, 11};
+static const BG_POINT OPTIONS_SOUND_SLIDER_START_POS           = { 5, 14};
+static const BG_POINT OPTIONS_MUSIC_SLIDER_END_POS             = {24, 11};
+static const BG_POINT OPTIONS_SOUND_SLIDER_END_POS             = {24, 14};
+static const u8       OPTIONS_MUSIC_SLIDER_SEGMENT_LENGTH      = (OPTIONS_MUSIC_SLIDER_END_POS.x - OPTIONS_MUSIC_SLIDER_START_POS.x + 1)
+                                                                    / VOLUME_OPTION_MAX;
+static const u8       OPTIONS_SOUND_SLIDER_SEGMENT_LENGTH      = (OPTIONS_SOUND_SLIDER_END_POS.x - OPTIONS_SOUND_SLIDER_START_POS.x + 1)
+                                                                    / VOLUME_OPTION_MAX;
+
+// Values in pixels
+static const BG_POINT OPTIONS_GAME_SPEED_TEXT_POS    = { 82,  16};
+static const BG_POINT OPTIONS_HIGH_CONTRAST_TEXT_POS = { 40,  48};
+static const BG_POINT OPTIONS_MUSIC_VOLUME_TEXT_POS  = { 56,  80};
+static const BG_POINT OPTIONS_MUSIC_VALUE_TEXT_POS   = {160,  80};
+static const BG_POINT OPTIONS_SOUND_VOLUME_TEXT_POS  = { 56, 104};
+static const BG_POINT OPTIONS_SOUND_VALUE_TEXT_POS   = {160, 104};
+static const BG_POINT OPTIONS_BACK_SAVE_TEXT_POS     = { 72, 136};
+// clang-format on
+
+#define GAME_SPEED_ARROW_HIGHLIGHT_DURATION 10
+enum OptionSpeedButtons game_speed_arrow_highlight_button = GAME_SPEED_UP_BTN_IDX;
+static s32 game_speed_arrow_highlight_start = UNDEFINED;
+
+static bool any_value_changed = false;
+static bool back_btn_is_save_state = false;
+
+static void disable_all_game_speed_outlines_except_self(enum OptionSpeedButtons highlighted_btn)
+{
+    for (int i = 0; i < NB_GAME_SPEED_BUTTONS; i++)
+    {
+        button_set_highlight(&game_speed_buttons[i], i == highlighted_btn);
+    }
+}
+
+static void disable_all_outlines_except_self(enum OptionButtons highlighted_btn)
+{
+    // These two get disabled no matter what here
+    disable_all_game_speed_outlines_except_self(NB_GAME_SPEED_BUTTONS);
+
+    for (int i = 0; i < NB_OPTIONS_BUTTONS; i++)
+    {
+        button_set_highlight(&options_menu_buttons[i], i == highlighted_btn);
+    }
+}
+
+static void update_game_speed_button_graphics()
+{
+    // check if need to disable game speed arrows
+    if (g_game_vars.game_speed == GAME_SPEED_MIN)
+    {
+        main_bg_se_copy_rect(
+            OPTIONS_SPEED_DOWN_DISABLED_BTN_SRC_RECT,
+            OPTIONS_SPEED_DOWN_BTN_DEST_POS
+        );
+    }
+    else
+    {
+        main_bg_se_copy_rect(
+            OPTIONS_SPEED_DOWN_ACTIVE_BTN_SRC_RECT,
+            OPTIONS_SPEED_DOWN_BTN_DEST_POS
+        );
+    }
+
+    if (g_game_vars.game_speed == GAME_SPEED_MAX)
+    {
+        main_bg_se_copy_rect(OPTIONS_SPEED_UP_DISABLED_BTN_SRC_RECT, OPTIONS_SPEED_UP_BTN_DEST_POS);
+    }
+    else
+    {
+        main_bg_se_copy_rect(OPTIONS_SPEED_UP_ACTIVE_BTN_SRC_RECT, OPTIONS_SPEED_UP_BTN_DEST_POS);
+    }
+
+    main_bg_se_copy_rect(
+        OPTIONS_SPEED_VALUES[g_game_vars.game_speed - 1],
+        OPTIONS_SPEED_VALUE_DEST_POS
+    );
+
+    any_value_changed = true;
+}
+
+static void update_high_contrast_button_graphics()
+{
+    if (g_game_vars.high_contrast)
+    {
+        main_bg_se_copy_rect(OPTIONS_CONTRAST_VALUE_YES_SRC_RECT, OPTIONS_CONTRAST_VALUE_DEST_POS);
+    }
+    else
+    {
+        main_bg_se_copy_rect(OPTIONS_CONTRAST_VALUE_NO_SRC_RECT, OPTIONS_CONTRAST_VALUE_DEST_POS);
+    }
+
+    any_value_changed = true;
+}
+
+static void update_volume_slider_graphics(enum OptionButtons slider_idx)
+{
+    u8 slider_value;
+    BG_POINT slider_segment_dest;
+    int slider_segment_length;
+    Rect slider_segment_full;
+    Rect slider_segment_mid;
+    Rect slider_segment_empty;
+    BG_POINT slider_text_pos;
+
+    switch (slider_idx)
+    {
+        case MUSIC_VOLUME_BTN_IDX:
+            slider_value = g_game_vars.music_volume;
+            slider_segment_dest = OPTIONS_MUSIC_SLIDER_START_POS;
+            slider_segment_length = OPTIONS_MUSIC_SLIDER_SEGMENT_LENGTH;
+            slider_segment_full = OPTIONS_MUSIC_SLIDER_FULL_SRC;
+            slider_segment_mid = OPTIONS_MUSIC_SLIDER_MID_SRC;
+            slider_segment_empty = OPTIONS_MUSIC_SLIDER_EMPTY_SRC;
+            slider_text_pos = OPTIONS_MUSIC_VALUE_TEXT_POS;
+            break;
+        case SOUND_VOLUME_BTN_IDX:
+            slider_value = g_game_vars.sound_volume;
+            slider_segment_dest = OPTIONS_SOUND_SLIDER_START_POS;
+            slider_segment_length = OPTIONS_SOUND_SLIDER_SEGMENT_LENGTH;
+            slider_segment_full = OPTIONS_SOUND_SLIDER_FULL_SRC;
+            slider_segment_mid = OPTIONS_SOUND_SLIDER_MID_SRC;
+            slider_segment_empty = OPTIONS_SOUND_SLIDER_EMPTY_SRC;
+            slider_text_pos = OPTIONS_SOUND_VALUE_TEXT_POS;
+            break;
+        // This function only takes in a volume slider
+        default:
+            return;
+    }
+
+    int i = 0;
+
+    // full part of the bar
+    for (; i < slider_value * slider_segment_length - 1; i++)
+    {
+        main_bg_se_copy_rect(slider_segment_full, slider_segment_dest);
+        slider_segment_dest.x++;
+    }
+
+    // at exactly `slider_value` we either:
+    //  - are in the middle of the bar, then we draw the frontier between full and empty tiles
+    //  - are at the end, then draw a full segment
+    if (slider_value == VOLUME_OPTION_MAX)
+    {
+        main_bg_se_copy_rect(slider_segment_full, slider_segment_dest);
+    }
+    else
+    {
+        if (slider_value != VOLUME_OPTION_MIN)
+        {
+            // draw middle point
+            main_bg_se_copy_rect(slider_segment_mid, slider_segment_dest);
+            i++;
+            slider_segment_dest.x++;
+        }
+
+        // empty part of the bar
+        for (; i < VOLUME_OPTION_MAX * slider_segment_length; i++)
+        {
+            main_bg_se_copy_rect(slider_segment_empty, slider_segment_dest);
+            slider_segment_dest.x++;
+        }
+    }
+
+    tte_printf(
+        "#{P:%d,%d; cx:0x%X000}%3d",
+        slider_text_pos.x,
+        slider_text_pos.y,
+        TTE_WHITE_PB,
+        (slider_value * VOLUME_OPTION_INCREMENT)
+    );
+
+    any_value_changed = true;
+}
+
+static void change_back_save_text(bool is_back)
+{
+    char* btn_text = is_back ? "    Back    " : "Save Changes";
+    tte_printf(
+        "#{P:%d,%d; cx:0x%X000}%s",
+        OPTIONS_BACK_SAVE_TEXT_POS.x,
+        OPTIONS_BACK_SAVE_TEXT_POS.y,
+        TTE_WHITE_PB,
+        btn_text
+    );
+}
+
+void game_options_menu_change_background(void)
+{
+    tte_erase_screen();
+    CBB_CLEAR(MAIN_BG_CBB);
+
+    GRIT_CPY(pal_bg_mem, background_options_menu_gfxPal);
+    GRIT_CPY(&tile_mem[MAIN_BG_CBB], background_options_menu_gfxTiles);
+    GRIT_CPY(&se_mem[MAIN_BG_SBB], background_options_menu_gfxMap);
+
+    tte_printf(
+        "#{P:%d,%d; cx:0x%X000}Game Speed",
+        OPTIONS_GAME_SPEED_TEXT_POS.x,
+        OPTIONS_GAME_SPEED_TEXT_POS.y,
+        TTE_WHITE_PB
+    );
+    tte_printf(
+        "#{P:%d,%d; cx:0x%X000}High Contrast Cards",
+        OPTIONS_HIGH_CONTRAST_TEXT_POS.x,
+        OPTIONS_HIGH_CONTRAST_TEXT_POS.y,
+        TTE_WHITE_PB
+    );
+    tte_printf(
+        "#{P:%d,%d; cx:0x%X000}Music Volume",
+        OPTIONS_MUSIC_VOLUME_TEXT_POS.x,
+        OPTIONS_MUSIC_VOLUME_TEXT_POS.y,
+        TTE_WHITE_PB
+    );
+    tte_printf(
+        "#{P:%d,%d; cx:0x%X000}Sound Volume",
+        OPTIONS_SOUND_VOLUME_TEXT_POS.x,
+        OPTIONS_SOUND_VOLUME_TEXT_POS.y,
+        TTE_WHITE_PB
+    );
+    change_back_save_text(true);
+}
+
+void game_options_menu_on_init(void)
+{
+    change_background(BG_OPTIONS_MENU);
+
+    // Select game speed button by default
+    options_menu_selection_grid.selection = OPTIONS_MENU_INIT_SEL;
+    disable_all_outlines_except_self(GAME_SPEED_BTN_IDX);
+
+    // Do an update on the first frame
+    update_game_speed_button_graphics();
+    update_high_contrast_button_graphics();
+    update_volume_slider_graphics(MUSIC_VOLUME_BTN_IDX);
+    update_volume_slider_graphics(SOUND_VOLUME_BTN_IDX);
+
+    // Prevent "Back" button to become "Save Changes" when we first load the data,
+    // the player hasn't technically changed anything so it would be confusing.
+    any_value_changed = false;
+}
+
+void game_options_menu_on_update(void)
+{
+    selection_grid_process_input(&options_menu_selection_grid);
+
+    // game speed arrows small animation: they stay highlighted for a few frames
+    if (game_speed_arrow_highlight_start != UNDEFINED &&
+        (g_game_vars.timer - game_speed_arrow_highlight_start) >
+            GAME_SPEED_ARROW_HIGHLIGHT_DURATION)
+    {
+        game_speed_arrow_highlight_start = UNDEFINED;
+        button_set_highlight(&game_speed_buttons[game_speed_arrow_highlight_button], false);
+    }
+
+    // Except on the first update where it is forced to display the loaded values
+    // instead of the default ones, if any value was changed, edit the last button
+    // text to read "Save Changes" instead of "Back"
+    if (any_value_changed && !back_btn_is_save_state)
+    {
+        change_back_save_text(false);
+        back_btn_is_save_state = true;
+    }
+
+    any_value_changed = false;
+}
+
+void game_options_menu_on_exit(void)
+{
+    tte_erase_screen();
+}
+
+static void game_speed_down_on_pressed(void)
+{
+    g_game_vars.game_speed--;
+    game_speed_arrow_highlight_start = g_game_vars.timer;
+    game_speed_arrow_highlight_button = GAME_SPEED_DOWN_BTN_IDX;
+    disable_all_game_speed_outlines_except_self(GAME_SPEED_DOWN_BTN_IDX);
+    update_game_speed_button_graphics();
+}
+
+static void game_speed_up_on_pressed(void)
+{
+    g_game_vars.game_speed++;
+    game_speed_arrow_highlight_start = g_game_vars.timer;
+    game_speed_arrow_highlight_button = GAME_SPEED_UP_BTN_IDX;
+    disable_all_game_speed_outlines_except_self(GAME_SPEED_UP_BTN_IDX);
+    update_game_speed_button_graphics();
+}
+
+/**
+ * @brief Handles input for the high contrast card toggle button and nothing more.
+ */
+static void high_contrast_on_pressed(void)
+{
+    g_game_vars.high_contrast = (g_game_vars.high_contrast == 1) ? false : true;
+    update_high_contrast_button_graphics();
+}
+
+/**
+ * @brief Handles input for the Back/Save button.
+ */
+static void back_on_pressed(void)
+{
+    if (back_btn_is_save_state)
+    {
+        save_game();
+        change_back_save_text(true);
+        back_btn_is_save_state = false;
+    }
+    else
+    {
+        game_change_state(GAME_STATE_MAIN_MENU);
+    }
+}
+
+/**
+ * @brief Gives the width of options menu rows in selection grid.
+ *
+ * @returns Always 1, all rows contain only 1 button. Could have been a define
+ *          but I had to make this a function so it could be given to the
+ *          SelectionGrid constructor.
+ */
+static int options_menu_return_row_size(void)
+{
+    return 1;
+}
+
+static void change_button_highlight(
+    int row_idx,
+    const Selection* prev_selection,
+    const Selection* new_selection
+)
+{
+    if (prev_selection->y == row_idx && prev_selection->x >= 0 &&
+        prev_selection->x < NB_OPTIONS_BUTTONS)
+    {
+        button_set_highlight(&options_menu_buttons[row_idx], false);
+    }
+
+    if (new_selection->y == row_idx)
+    {
+        play_sfx(SFX_BUTTON, MM_BASE_PITCH_RATE, BUTTON_SFX_VOLUME);
+        button_set_highlight(&options_menu_buttons[row_idx], true);
+    }
+}
+
+/**
+ * @brief Handles left/Right inputs on the row of the Game Speed button.
+ *        Is used to increased/decrease the speed value, instead of relying on a
+ *        `on_key_transit` function because the latter does not take directional
+ *        inputs.
+ */
+static bool game_speed_row_on_selection_changed(
+    SelectionGrid* selection_grid,
+    int row_idx,
+    const Selection* prev_selection,
+    const Selection* new_selection
+)
+{
+    change_button_highlight(row_idx, prev_selection, new_selection);
+    disable_all_game_speed_outlines_except_self(NB_GAME_SPEED_BUTTONS);
+
+    // Can only change game speed by pressing left/right while staying on the button's row
+    if (prev_selection->y != new_selection->y)
+        return true;
+
+    if (key_hit(KEY_LEFT) && g_game_vars.game_speed > GAME_SPEED_MIN)
+    {
+        button_press(&game_speed_buttons[GAME_SPEED_DOWN_BTN_IDX]);
+    }
+    else if (key_hit(KEY_RIGHT) && g_game_vars.game_speed < GAME_SPEED_MAX)
+    {
+        button_press(&game_speed_buttons[GAME_SPEED_UP_BTN_IDX]);
+    }
+
+    return true;
+}
+
+/**
+ * @brief Handles input for all SelectionGridRows in options menu, only actually does
+ *        something on rows containing "normal" buttons (those for which the on_pressed
+ *        method in options_menu_buttons is not NULL).
+ */
+static void options_menu_row_on_key_transit(SelectionGrid* selection_grid, Selection* selection)
+{
+    if (key_hit(SELECT_CARD))
+    {
+        button_press(&options_menu_buttons[selection->y]);
+    }
+}
+
+static bool regular_button_row_on_selection_changed(
+    SelectionGrid* selection_grid,
+    int row_idx,
+    const Selection* prev_selection,
+    const Selection* new_selection
+)
+{
+    change_button_highlight(row_idx, prev_selection, new_selection);
+    return true;
+}
+
+static bool music_volume_row_on_selection_changed(
+    SelectionGrid* selection_grid,
+    int row_idx,
+    const Selection* prev_selection,
+    const Selection* new_selection
+)
+{
+    change_button_highlight(row_idx, prev_selection, new_selection);
+
+    if (prev_selection->y != new_selection->y)
+        return true;
+
+    if (key_hit(KEY_LEFT) && g_game_vars.music_volume > VOLUME_OPTION_MIN)
+    {
+        g_game_vars.music_volume--;
+    }
+    else if (key_hit(KEY_RIGHT) && g_game_vars.music_volume < VOLUME_OPTION_MAX)
+    {
+        g_game_vars.music_volume++;
+    }
+
+    update_volume_slider_graphics(MUSIC_VOLUME_BTN_IDX);
+    mmSetModuleVolume(MM_MODULE_FULL_VOLUME * g_game_vars.music_volume / VOLUME_OPTION_MAX);
+
+    return true;
+}
+
+static bool sound_volume_row_on_selection_changed(
+    SelectionGrid* selection_grid,
+    int row_idx,
+    const Selection* prev_selection,
+    const Selection* new_selection
+)
+{
+    change_button_highlight(row_idx, prev_selection, new_selection);
+
+    if (prev_selection->y != new_selection->y)
+        return true;
+
+    if (key_hit(KEY_LEFT) && g_game_vars.sound_volume > VOLUME_OPTION_MIN)
+    {
+        g_game_vars.sound_volume--;
+    }
+    else if (key_hit(KEY_RIGHT) && g_game_vars.sound_volume < VOLUME_OPTION_MAX)
+    {
+        g_game_vars.sound_volume++;
+    }
+
+    update_volume_slider_graphics(SOUND_VOLUME_BTN_IDX);
+
+    return true;
+}

source/joker.c

@@ -1,6 +1,7 @@
 #include "joker.h"
 
 #include "card.h"
+#include "game_variables.h"
 #include "graphic_utils.h"
 #include "joker_gfx.h"
 #include "pool.h"
@@ -271,7 +272,7 @@ bool joker_object_score(
 
     u32 chips = get_chips();
     u32 mult = get_mult();
-    int money = get_money();
+    int money = g_game_vars.money;
 
     if (effect_flags_ret & JOKER_EFFECT_FLAG_RETRIGGER)
     {
@@ -345,7 +346,7 @@ bool joker_object_score(
     // Update values
     set_chips(chips);
     set_mult(mult);
-    set_money(money);
+    g_game_vars.money = money;
 
     // Update displays
     display_chips();
@@ -367,7 +368,7 @@ Sprite* joker_object_get_sprite(JokerObject* joker_object)
 int joker_get_random_rarity()
 {
     int joker_rarity = 0;
-    int rarity_roll = random() % 100;
+    int rarity_roll = get_rand() % 100;
     if (rarity_roll < COMMON_JOKER_CHANCE)
     {
         joker_rarity = COMMON_JOKER;

source/joker_effects.c

@@ -562,7 +562,7 @@ static u32 misprint_joker_effect(
 
     *joker_effect = &shared_joker_effect;
 
-    (*joker_effect)->mult = random() % (MISPRINT_MAX_MULT + 1);
+    (*joker_effect)->mult = get_rand() % (MISPRINT_MAX_MULT + 1);
 
     return JOKER_EFFECT_FLAG_MULT;
 }
@@ -775,7 +775,7 @@ static u32 reserved_parking_joker_effect(
 
     u32 effect_flags_ret = JOKER_EFFECT_FLAG_NONE;
 
-    if ((random() % 2 == 0) && card_is_face(scored_card))
+    if ((get_rand() % 2 == 0) && card_is_face(scored_card))
     {
         *joker_effect = &shared_joker_effect;
 
@@ -797,7 +797,7 @@ static u32 business_card_joker_effect(
 
     u32 effect_flags_ret = JOKER_EFFECT_FLAG_NONE;
 
-    if ((random() % 2 == 0) && card_is_face(scored_card))
+    if ((get_rand() % 2 == 0) && card_is_face(scored_card))
     {
         *joker_effect = &shared_joker_effect;
 
@@ -885,11 +885,11 @@ static u32 bull_joker_effect(
 
     // The wiki says it does nothing if money is 0 or below
     // This allows us to avoid scoring negative Chips
-    if (get_money() > 0)
+    if (g_game_vars.money > 0)
     {
         *joker_effect = &shared_joker_effect;
 
-        (*joker_effect)->chips = get_money() * 2;
+        (*joker_effect)->chips = g_game_vars.money * 2;
         effect_flags_ret = JOKER_EFFECT_FLAG_CHIPS;
     }
 
@@ -1154,11 +1154,11 @@ static u32 bootstraps_joker_effect(
     u32 effect_flags_ret = JOKER_EFFECT_FLAG_NONE;
 
     // Same protection as the Bull Joker
-    if (get_money() > 0)
+    if (g_game_vars.money > 0)
     {
         *joker_effect = &shared_joker_effect;
 
-        (*joker_effect)->mult = (get_money() / 5) * 2;
+        (*joker_effect)->mult = (g_game_vars.money / 5) * 2;
         effect_flags_ret = JOKER_EFFECT_FLAG_MULT;
     }
 

source/save.c

@@ -0,0 +1,166 @@
+/**
+ * @file save.c
+ */
+#include "save.h"
+
+#include "audio_utils.h"
+#include "game.h"
+#include "joker.h"
+#include "list.h"
+#include "util.h"
+#include "version.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+// See https://gbadev.net/gbadoc/memory.html for more details on SRAM
+// A few important pieces of info:
+//   - Read/Writes are limited to 8-bits words so they are done byte per byte
+//   - Memory is filled with 1s by default
+//     (at least in mgba, not sure about real HW)
+
+#define CHECK_BASE 0x0000
+#define GAME_BASE  0x0010
+#define LISTS_BASE 0x0060
+
+#define CHECK_MAGIC     0x4C414247 // Spells GBAL, used to determine if the save data is junk
+#define CHECK_HASH_SIZE 7
+#define GIT_HASH_START  17 // starts after "GBALATRO-VERSION:" in the gbalatro_version var
+
+// clang-format off
+/**
+ * @brief SaveHeader for validation checks
+ *
+ * Structure holding save data header info to be packed and written to SRAM for validation.
+ * Defined in this discussion as follows: https://github.com/GBALATRO/balatro-gba/discussions/450
+ * word | Byte 0 | Byte 1 | Byte 2 | Byte 3 | name         | purpose
+ * -----|--------|--------|--------|--------|--------------|------------------------------------------------------------------
+ * 0    | 0x47   | 0x42   | 0x41   | 0x4C   | MAGIC        | Identify if proceeding data is valid and not junk, spells "GBAL"
+ * 1    | Dirty  | H[0]   | H[1]   | H[2]   | GITHASH_LOW  | Dirty flag, followed by the first 3 bytes of shortened git hash H
+ * 2    | H[3]   | H[4]   | H[5]   | H[6]   | GITHASH_HIGH | Last 4 bytes of shortened git hash H, with a dirty flag
+ */
+// clang-format on
+typedef struct SaveHeader
+{
+    u32 magic;
+    bool dirty;
+    char githash[CHECK_HASH_SIZE];
+} SaveHeader;
+
+/**
+ * @brief Write raw binary data to SRAM
+ *
+ * @param sram_base address written to in the SRAM
+ * @param bytes pointer to the written data
+ * @param size number of bytes written
+ */
+static inline void write_sram(u32 sram_base, const u8* bytes, u32 size)
+{
+    if (sram_base + size > SRAM_SIZE)
+        return;
+
+    for (u32 i = 0; i < size; i++)
+    {
+        sram_mem[sram_base + i] = bytes[i];
+    }
+}
+
+/**
+ * @brief Read raw binary data from SRAM
+ *
+ * @sa write_sram
+ */
+static inline void read_sram(u32 sram_base, u8* bytes, u32 size)
+{
+    if (sram_base + size > SRAM_SIZE)
+        return;
+
+    for (u32 i = 0; i < size; i++)
+    {
+        bytes[i] = sram_mem[sram_base + i];
+    }
+}
+
+/**
+ * @brief Checks the 7 chars of gbalatro_version after the "GBALATRO_VERSION" prefix
+ *         representing the git hash of the code the build is based on.
+ *
+ * @returns true if the git hash of the ROM is equal to the hash saved in SRAM.
+ *          false if they are different.
+ */
+static inline bool check_hash(const char* prefix)
+{
+    for (u32 i = 0; i < CHECK_HASH_SIZE; i++)
+    {
+        if (gbalatro_version[GIT_HASH_START + i] != prefix[i])
+        {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+/**
+ * @brief Determines if the current build is considered "dirty" aka has uncommitted changes.
+ *         This works because the gbalatro_version string has "-dirty" added at the end if it's
+ *         dirty.
+ *
+ * @returns true if version is dirty, false otherwise.
+ */
+static inline bool is_version_dirty()
+{
+    return strlen(gbalatro_version) > GIT_HASH_START + CHECK_HASH_SIZE;
+}
+
+/**
+ * @brief Writes a magic number and ROM version info to SRAM to signal that the
+ *         save data exists and allow the game to determine if it is compatible.
+ */
+static inline void set_save_header()
+{
+    SaveHeader check = {};
+    check.magic = CHECK_MAGIC;
+    check.dirty = is_version_dirty();
+    memcpy(&(check.githash), gbalatro_version + GIT_HASH_START, CHECK_HASH_SIZE);
+
+    write_sram(CHECK_BASE, (const u8*)&check, sizeof(check));
+}
+
+/**
+ * @brief Reads whether the save data exists and is valid.
+ *
+ * @sa set_save_valid
+ */
+static inline bool check_save_header()
+{
+    SaveHeader check;
+    read_sram(CHECK_BASE, (u8*)&check, sizeof(check));
+
+    bool is_valid = (check.magic == CHECK_MAGIC) && check.dirty == is_version_dirty() &&
+                    check_hash(check.githash);
+
+    return is_valid;
+}
+
+void save_game(void)
+{
+    set_save_header();
+    write_sram(GAME_BASE, (const u8*)&g_game_vars, sizeof(g_game_vars));
+}
+
+void load_game(void)
+{
+    if (!check_save_header())
+        return;
+
+    read_sram(GAME_BASE, (u8*)&g_game_vars, sizeof(g_game_vars));
+
+    // return to where we were in the random sequence so that the run stays reproducible
+    for (u32 i = 0; i < g_game_vars.rng_step; i++)
+    {
+        (void)rand();
+    }
+
+    mmSetModuleVolume(MM_MODULE_FULL_VOLUME * g_game_vars.music_volume / VOLUME_OPTION_MAX);
+}

source/selection_grid.c

@@ -125,6 +125,9 @@ void selection_grid_process_input(SelectionGrid* selection_grid)
     {
         // To make the next line shorter and more readable
         Selection* selection = &selection_grid->selection;
-        selection_grid->rows[selection->y].on_key_transit(selection_grid, selection);
+        if (selection_grid->rows[selection->y].on_key_transit != NULL)
+        {
+            selection_grid->rows[selection->y].on_key_transit(selection_grid, selection);
+        }
     }
 }

source/splash_screen.c

@@ -11,7 +11,7 @@
 static const Rect COUNTDOWN_TIMER_RECT = {208, 144, 240, 152};
 static uint timer = 0;
 
-void splash_screen_on_init()
+void splash_screen_on_init(void)
 {
     timer = 0;
 
@@ -25,7 +25,7 @@ void splash_screen_on_init()
     tte_printf("#{P:8,144; cx:0xF000}(Press any key to skip)");
 }
 
-void splash_screen_on_update()
+void splash_screen_on_update(void)
 {
     timer++;
 
@@ -49,7 +49,7 @@ void splash_screen_on_update()
     tte_erase_screen();
 }
 
-void splash_screen_on_exit()
+void splash_screen_on_exit(void)
 {
     mmStart(MOD_MAIN_THEME, MM_PLAY_LOOP);
 }

source/sprite.c

@@ -2,6 +2,7 @@
 
 #include "audio_utils.h"
 #include "game.h"
+#include "game_variables.h"
 #include "pool.h"
 #include "soundbank.h"
 #include "util.h"
@@ -209,8 +210,8 @@ void sprite_object_reset_transform(SpriteObject* sprite_object)
 
 void sprite_object_update(SpriteObject* sprite_object)
 {
-    sprite_object->vx += ((sprite_object->tx - sprite_object->x) * get_game_speed()) / 8;
-    sprite_object->vy += ((sprite_object->ty - sprite_object->y) * get_game_speed()) / 8;
+    sprite_object->vx += ((sprite_object->tx - sprite_object->x) * g_game_vars.game_speed) / 8;
+    sprite_object->vy += ((sprite_object->ty - sprite_object->y) * g_game_vars.game_speed) / 8;
 
     // Scale up the card when it's played
     sprite_object->vscale += (sprite_object->tscale - sprite_object->scale) / 8;
@@ -310,7 +311,7 @@ void sprite_object_set_focus(SpriteObject* sprite_object, bool focus)
 
     play_sfx(
         SFX_CARD_FOCUS,
-        MM_BASE_PITCH_RATE + rand() % CARD_FOCUS_SFX_PITCH_OFFSET_RANGE,
+        MM_BASE_PITCH_RATE + get_rand() % CARD_FOCUS_SFX_PITCH_OFFSET_RANGE,
         SFX_DEFAULT_VOLUME
     );
     sprite_object->ty = sprite_object->ty + int2fx((focus ? -1 : 1) * SPRITE_FOCUS_RAISE_PX);

source/version.c

@@ -6,5 +6,5 @@
 #define GIT_DIRTY "-dirty"
 #endif
 
-__attribute__((section(".version"), used)) const char balatro_version[] =
-    "GBALATRO_VERSION:" GIT_HASH GIT_DIRTY;
+__attribute__((section(".version"), used)) const char gbalatro_version[] =
+    "GBALATRO-VERSION:" GIT_HASH GIT_DIRTY;