refactor main.c and start with black hole gravity implementation

src/game.c

@@ -0,0 +1,223 @@
+/*
+ * game.c
+ * Duality
+ *
+ * Copyright (C) 2025 Thomas Buck <thomas@xythobuz.de>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * See <http://www.gnu.org/licenses/>.
+ */
+
+#include <gbdk/platform.h>
+#include <gbdk/metasprites.h>
+#include <rand.h>
+#include <stdint.h>
+
+#include "maps.h"
+#include "obj.h"
+#include "sprites.h"
+#include "sound.h"
+#include "input.h"
+#include "game.h"
+
+enum ACCELERATION {
+    ACC_X = 1,
+    ACC_Y = 2,
+    ACC_R = 4,
+};
+
+#define BAR_OFFSET_X (4 - 80)
+#define HEALTH_OFFSET_Y -16
+#define POWER_OFFSET_Y 16
+
+static void status(uint8_t health, uint8_t power, uint8_t *hiwater) {
+    if (health > 0) {
+        switch (health >> 6) {
+            case 3:
+                spr_draw(SPR_HEALTH, FLIP_X, BAR_OFFSET_X, HEALTH_OFFSET_Y - 24, hiwater);
+            case 2:
+                spr_draw(SPR_HEALTH, FLIP_X, BAR_OFFSET_X, HEALTH_OFFSET_Y - 16, hiwater);
+            case 1:
+                spr_draw(SPR_HEALTH, FLIP_X, BAR_OFFSET_X, HEALTH_OFFSET_Y - 8, hiwater);
+            case 0:
+                spr_draw(SPR_HEALTH, FLIP_X, BAR_OFFSET_X, HEALTH_OFFSET_Y - 0, hiwater);
+        }
+    }
+
+    if (power > 0) {
+        switch (power >> 6) {
+            case 3:
+                spr_draw(SPR_POWER, FLIP_X, BAR_OFFSET_X, POWER_OFFSET_Y + 0, hiwater);
+            case 2:
+                spr_draw(SPR_POWER, FLIP_X, BAR_OFFSET_X, POWER_OFFSET_Y + 8, hiwater);
+            case 1:
+                spr_draw(SPR_POWER, FLIP_X, BAR_OFFSET_X, POWER_OFFSET_Y + 16, hiwater);
+            case 0:
+                spr_draw(SPR_POWER, FLIP_X, BAR_OFFSET_X, POWER_OFFSET_Y + 24, hiwater);
+        }
+    }
+}
+
+void game(void) {
+    disable_interrupts();
+    DISPLAY_OFF;
+    map_game();
+    SHOW_BKG;
+    SHOW_SPRITES;
+    SPRITES_8x8;
+    DISPLAY_ON;
+    enable_interrupts();
+
+    int16_t pos_x = 0;
+    int16_t pos_y = 0;
+    int16_t spd_x = 0;
+    int16_t spd_y = 0;
+    enum SPRITE_ROT rot = 0;
+    enum ACCELERATION prev_acc = 0xFF; // so we draw the ship on the first frame
+    uint8_t ship_hiwater = 0;
+    uint8_t health = HEALTH_MAX;
+    uint16_t power = POWER_MAX;
+
+    obj_init();
+
+    // TODO remove
+    obj_add(SPR_LIGHT, 64, 64, 0, 0);
+    //obj_add(SPR_DARK, -64, -64, 0, 0);
+    obj_add(SPR_DARK, -32, 0, 0, 0);
+    obj_add(SPR_SHOT_LIGHT, 32, 32, 0, 0);
+    obj_add(SPR_SHOT_DARK, -32, -32, 0, 0);
+
+    while(1) {
+        key_read();
+
+        enum ACCELERATION acc = 0;
+
+        if (key_pressed(J_LEFT)) {
+            rot = (rot - 1) & (ROT_INVALID - 1);
+            acc |= ACC_R;
+        } else if (key_pressed(J_RIGHT)) {
+            rot = (rot + 1) & (ROT_INVALID - 1);
+            acc |= ACC_R;
+        }
+
+        if (key_down(J_A) && (power > 0)) {
+            if (power >= POWER_DEC) {
+                power -= POWER_DEC;
+            } else {
+                power = 0;
+            }
+
+            switch (rot) {
+                case ROT_0:
+                    spd_y -= SPEED_INC;
+                    if (spd_y < -SPEED_MAX_ACC) spd_y = -SPEED_MAX_ACC;
+                    acc |= ACC_Y;
+                    break;
+
+                case ROT_90:
+                    spd_x += SPEED_INC;
+                    if (spd_x > SPEED_MAX_ACC) spd_x = SPEED_MAX_ACC;
+                    acc |= ACC_X;
+                    break;
+
+                case ROT_180:
+                    spd_y += SPEED_INC;
+                    if (spd_y > SPEED_MAX_ACC) spd_y = SPEED_MAX_ACC;
+                    acc |= ACC_Y;
+                    break;
+
+                case ROT_270:
+                    spd_x -= SPEED_INC;
+                    if (spd_x < -SPEED_MAX_ACC) spd_x = -SPEED_MAX_ACC;
+                    acc |= ACC_X;
+                    break;
+
+                default:
+                    break;
+            }
+        } else if (!key_down(J_A) && (power < POWER_MAX)) {
+            if (power <= (POWER_MAX - POWER_INC)) {
+                power += POWER_INC;
+            } else {
+                power = POWER_MAX;
+            }
+        }
+
+        // TODO
+        //obj_act(pos_x, pos_y, &spd_x, &spd_y);
+
+        // adjust speed down when not moving
+        if (!(acc & ACC_X)) {
+            if (spd_x != 0) {
+                if (spd_x > SPEED_MAX_IDLE) spd_x -= SPEED_DEC;
+                else if (spd_x < -SPEED_MAX_IDLE) spd_x += SPEED_DEC;
+            }
+        }
+        if (!(acc & ACC_Y)) {
+            if (spd_y != 0) {
+                if (spd_y > SPEED_MAX_IDLE) spd_y -= SPEED_DEC;
+                else if (spd_y < -SPEED_MAX_IDLE) spd_y += SPEED_DEC;
+            }
+        }
+
+        if (key_pressed(J_B)) {
+            int8_t ret = -1;
+            switch (rot) {
+                case ROT_0:
+                    ret = obj_add(SPR_SHOT, 0, -SHIP_OFF, spd_x, spd_y - SHOT_SPEED);
+                    break;
+
+                case ROT_90:
+                    ret = obj_add(SPR_SHOT, SHIP_OFF, 0, spd_x + SHOT_SPEED, spd_y);
+                    break;
+
+                case ROT_180:
+                    ret = obj_add(SPR_SHOT, 0, SHIP_OFF, spd_x, spd_y + SHOT_SPEED);
+                    break;
+
+                case ROT_270:
+                    ret = obj_add(SPR_SHOT, -SHIP_OFF, 0, spd_x - SHOT_SPEED, spd_y);
+                    break;
+
+                default:
+                    break;
+            }
+
+            if (ret == OBJ_ADDED) {
+                snd_noise();
+            }
+        }
+
+        pos_x += spd_x;
+        pos_y += spd_y;
+        move_bkg(pos_x >> POS_SCALE_BG, pos_y >> POS_SCALE_BG);
+
+        uint8_t hiwater = SPR_NUM_START;
+
+        // re-draw ship sprite when we've just rotated or are starting or stopping acceleration
+        if ((acc & ACC_R) || ((prev_acc & (ACC_X | ACC_Y)) != (acc & (ACC_X | ACC_Y)))) {
+            spr_ship(rot, acc & (ACC_X | ACC_Y), &hiwater);
+            ship_hiwater = hiwater;
+        } else {
+            hiwater = ship_hiwater;
+        }
+
+        obj_draw(spd_x, spd_y, &hiwater);
+        status(health, power >> POWER_SHIFT, &hiwater);
+
+        hide_sprites_range(hiwater, MAX_HARDWARE_SPRITES);
+
+        prev_acc = acc;
+
+        vsync();
+    }
+}

src/game.h

@@ -0,0 +1,44 @@
+/*
+ * game.h
+ * Duality
+ *
+ * Copyright (C) 2025 Thomas Buck <thomas@xythobuz.de>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * See <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GAME_H__
+#define __GAME_H__
+
+#define SPEED_INC 1
+#define SPEED_DEC 1
+
+#define SPEED_MAX_ACC 16
+#define SPEED_MAX_IDLE 12
+
+#define POS_SCALE_OBJS 5
+#define POS_SCALE_BG 6
+
+#define POWER_MAX 0x1FF
+#define POWER_SHIFT 1
+
+#define POWER_INC 2
+#define POWER_DEC 4
+
+#define HEALTH_MAX 0xFF
+
+#define SHOT_SPEED 23
+
+void game(void);
+
+#endif // __GAME_H__

src/input.c

@@ -0,0 +1,38 @@
+/*
+ * input.c
+ * Duality
+ *
+ * Copyright (C) 2025 Thomas Buck <thomas@xythobuz.de>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * See <http://www.gnu.org/licenses/>.
+ */
+
+#include <gbdk/platform.h>
+
+#include "input.h"
+
+static uint8_t joyp = 0;
+static uint8_t old_joyp = 0;
+
+void key_read(void) {
+    old_joyp = joyp;
+    joyp = joypad();
+}
+
+uint8_t key_down(uint8_t key) {
+    return joyp & key;
+}
+
+uint8_t key_pressed(uint8_t key) {
+    return (joyp ^ old_joyp) & joyp & key;
+}

src/input.h

@@ -0,0 +1,29 @@
+/*
+ * input.h
+ * Duality
+ *
+ * Copyright (C) 2025 Thomas Buck <thomas@xythobuz.de>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * See <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __INPUT_H__
+#define __INPUT_H__
+
+#include <stdint.h>
+
+void key_read(void);
+uint8_t key_down(uint8_t key);
+uint8_t key_pressed(uint8_t key);
+
+#endif // __INPUT_H__

src/main.c

@@ -29,29 +29,8 @@
 #include "obj.h"
 #include "sprites.h"
 #include "sound.h"
-
-#define SPR_NUM_START 0
-
-static uint8_t joyp = 0;
-static uint8_t old_joyp = 0;
-
-#define KEY_INPUT (old_joyp = joyp, joyp = joypad())
-#define KEY_DOWN(KEY) (joyp & (KEY))
-#define KEY_PRESSED(KEY) ((joyp ^ old_joyp) & joyp & (KEY))
-
-enum ACCELERATION {
-    ACC_X = 1,
-    ACC_Y = 2,
-    ACC_R = 4,
-};
-
-#define SPEED_INC 1
-#define SPEED_MAX 16
-#define SHOT_SPEED 23
-
-#define BAR_OFFSET_X (4 - 80)
-#define HEALTH_OFFSET_Y -16
-#define POWER_OFFSET_Y 16
+#include "input.h"
+#include "game.h"
 
 static void splash(void) {
     disable_interrupts();
@@ -68,8 +47,8 @@ static void splash(void) {
     obj_add(SPR_DARK, -42, -42, 0, 0);
 
     while(1) {
-        KEY_INPUT;
-        if (KEY_DOWN(0xFF)) {
+        key_read();
+        if (key_down(0xFF)) {
             break;
         }
 
@@ -81,162 +60,6 @@ static void splash(void) {
     }
 }
 
-static void status(uint8_t health, uint8_t power, uint8_t *hiwater) {
-    if (health > 0) {
-        switch (health >> 6) {
-            case 3:
-                spr_draw(SPR_HEALTH, FLIP_X, BAR_OFFSET_X, HEALTH_OFFSET_Y - 24, hiwater);
-            case 2:
-                spr_draw(SPR_HEALTH, FLIP_X, BAR_OFFSET_X, HEALTH_OFFSET_Y - 16, hiwater);
-            case 1:
-                spr_draw(SPR_HEALTH, FLIP_X, BAR_OFFSET_X, HEALTH_OFFSET_Y - 8, hiwater);
-            case 0:
-                spr_draw(SPR_HEALTH, FLIP_X, BAR_OFFSET_X, HEALTH_OFFSET_Y - 0, hiwater);
-        }
-    }
-
-    if (power > 0) {
-        switch (power >> 6) {
-            case 3:
-                spr_draw(SPR_POWER, FLIP_X, BAR_OFFSET_X, POWER_OFFSET_Y + 0, hiwater);
-            case 2:
-                spr_draw(SPR_POWER, FLIP_X, BAR_OFFSET_X, POWER_OFFSET_Y + 8, hiwater);
-            case 1:
-                spr_draw(SPR_POWER, FLIP_X, BAR_OFFSET_X, POWER_OFFSET_Y + 16, hiwater);
-            case 0:
-                spr_draw(SPR_POWER, FLIP_X, BAR_OFFSET_X, POWER_OFFSET_Y + 24, hiwater);
-        }
-    }
-}
-
-static void game(void) {
-    disable_interrupts();
-    DISPLAY_OFF;
-    map_game();
-    SHOW_BKG;
-    SHOW_SPRITES;
-    SPRITES_8x8;
-    DISPLAY_ON;
-    enable_interrupts();
-
-    int16_t PosX = 0;
-    int16_t PosY = 0;
-    int16_t SpdX = 0;
-    int16_t SpdY = 0;
-    enum SPRITE_ROT rot = 0;
-    enum ACCELERATION prev_acc = 0xFF; // so we draw the ship on the first frame
-    uint8_t ship_hiwater = 0;
-    uint8_t health = 0xFF;
-    uint8_t power = 0xFF;
-
-    obj_init();
-
-    // TODO remove
-    obj_add(SPR_LIGHT, 64, 64, 0, 0);
-    obj_add(SPR_DARK, -64, -64, 0, 0);
-    obj_add(SPR_SHOT_LIGHT, 32, 32, 0, 0);
-    obj_add(SPR_SHOT_DARK, -32, -32, 0, 0);
-
-    while(1) {
-        KEY_INPUT;
-
-        enum ACCELERATION acc = 0;
-
-        if (KEY_PRESSED(J_LEFT)) {
-            rot = (rot - 1) & (ROT_INVALID - 1);
-            acc |= ACC_R;
-        } else if (KEY_PRESSED(J_RIGHT)) {
-            rot = (rot + 1) & (ROT_INVALID - 1);
-            acc |= ACC_R;
-        }
-
-        if (KEY_DOWN(J_A) && (power > 0)) {
-            power--;
-            switch (rot) {
-                case ROT_0:
-                    SpdY -= SPEED_INC;
-                    if (SpdY < -SPEED_MAX) SpdY = -SPEED_MAX;
-                    acc |= ACC_Y;
-                    break;
-
-                case ROT_90:
-                    SpdX += SPEED_INC;
-                    if (SpdX > SPEED_MAX) SpdX = SPEED_MAX;
-                    acc |= ACC_X;
-                    break;
-
-                case ROT_180:
-                    SpdY += SPEED_INC;
-                    if (SpdY > SPEED_MAX) SpdY = SPEED_MAX;
-                    acc |= ACC_Y;
-                    break;
-
-                case ROT_270:
-                    SpdX -= SPEED_INC;
-                    if (SpdX < -SPEED_MAX) SpdX = -SPEED_MAX;
-                    acc |= ACC_X;
-                    break;
-
-                default:
-                    break;
-            }
-        } else if (!KEY_DOWN(J_A) && (power < 0xFF)) {
-            power++;
-        }
-
-        if (KEY_PRESSED(J_B)) {
-            int8_t ret = -1;
-            switch (rot) {
-                case ROT_0:
-                    ret = obj_add(SPR_SHOT, 0, -SHIP_OFF, SpdX, SpdY - SHOT_SPEED);
-                break;
-
-                case ROT_90:
-                    ret = obj_add(SPR_SHOT, SHIP_OFF, 0, SpdX + SHOT_SPEED, SpdY);
-                break;
-
-                case ROT_180:
-                    ret = obj_add(SPR_SHOT, 0, SHIP_OFF, SpdX, SpdY + SHOT_SPEED);
-                break;
-
-                case ROT_270:
-                    ret = obj_add(SPR_SHOT, -SHIP_OFF, 0, SpdX - SHOT_SPEED, SpdY);
-                break;
-
-                default:
-                    break;
-            }
-
-            if (ret == OBJ_ADDED) {
-                snd_noise();
-            }
-        }
-
-        PosX += SpdX;
-        PosY += SpdY;
-        move_bkg(PosX >> 4, PosY >> 4);
-
-        uint8_t hiwater = SPR_NUM_START;
-
-        // re-draw ship sprite when we've just rotated or are starting or stopping acceleration
-        if ((acc & ACC_R) || ((prev_acc & (ACC_X | ACC_Y)) != (acc & (ACC_X | ACC_Y)))) {
-            spr_ship(rot, acc & (ACC_X | ACC_Y), &hiwater);
-            ship_hiwater = hiwater;
-        } else {
-            hiwater = ship_hiwater;
-        }
-
-        obj_draw(SpdX, SpdY, &hiwater);
-        status(health, power, &hiwater);
-
-        hide_sprites_range(hiwater, MAX_HARDWARE_SPRITES);
-
-        prev_acc = acc;
-
-        vsync();
-    }
-}
-
 void main(void) {
     spr_init();
     snd_init();

src/obj.c

@@ -21,8 +21,10 @@
 #include <string.h>
 #include <stdlib.h>
 
-#include "obj.h"
+#include "gb/hardware.h"
 #include "sprites.h"
+#include "game.h"
+#include "obj.h"
 
 /*
  * sprite budget:
@@ -104,8 +106,8 @@ enum OBJ_STATE obj_add(enum SPRITES sprite, int16_t off_x, int16_t off_y, int16_
 
     objs[obj_cnt].active = 1;
     objs[obj_cnt].sprite = sprite;
-    objs[obj_cnt].off_x = off_x << 4;
-    objs[obj_cnt].off_y = off_y << 4;
+    objs[obj_cnt].off_x = off_x << POS_SCALE_OBJS;
+    objs[obj_cnt].off_y = off_y << POS_SCALE_OBJS;
     objs[obj_cnt].spd_x = spd_x;
     objs[obj_cnt].spd_y = spd_y;
     objs[obj_cnt].travel = 0;
@@ -114,13 +116,32 @@ enum OBJ_STATE obj_add(enum SPRITES sprite, int16_t off_x, int16_t off_y, int16_
     return OBJ_ADDED;
 }
 
-void obj_draw(int16_t spd_x, int16_t spd_y, uint8_t *hiwater) {
+void obj_act(int16_t pos_x, int16_t pos_y, int16_t *spd_off_x, int16_t *spd_off_y) {
+    pos_x += DEVICE_SPRITE_PX_OFFSET_X + (DEVICE_SCREEN_PX_WIDTH / 2) - 16;
+    pos_y += DEVICE_SPRITE_PX_OFFSET_Y + (DEVICE_SCREEN_PX_HEIGHT / 2);
+
     for (uint8_t i = 0; i < MAX_OBJ; i++) {
         if (!objs[i].active) {
             continue;
         }
 
-        spr_draw(objs[i].sprite, FLIP_NONE, objs[i].off_x >> 4, objs[i].off_y >> 4, hiwater);
+        switch (objs[i].sprite) {
+            case SPR_DARK: {
+                *spd_off_x += (objs[i].off_x - pos_x) >> 8;
+                *spd_off_y += (objs[i].off_y - pos_y) >> 8;
+            } break;
+
+            default:
+                break;
+        }
+    }
+}
+
+void obj_draw(int16_t spd_x, int16_t spd_y, uint8_t *hiwater) {
+    for (uint8_t i = 0; i < MAX_OBJ; i++) {
+        if (!objs[i].active) {
+            continue;
+        }
 
         // move objects by their speed and compensate for movement of the background / ship
         objs[i].off_x += objs[i].spd_x - spd_x;
@@ -135,5 +156,7 @@ void obj_draw(int16_t spd_x, int16_t spd_y, uint8_t *hiwater) {
         if (objs[i].travel >= MAX_TRAVEL) {
             objs[i].active = 0;
         }
+
+        spr_draw(objs[i].sprite, FLIP_NONE, objs[i].off_x >> POS_SCALE_OBJS, objs[i].off_y >> POS_SCALE_OBJS, hiwater);
     }
 }

src/obj.h

@@ -31,6 +31,7 @@ enum OBJ_STATE {
 
 void obj_init(void);
 enum OBJ_STATE obj_add(enum SPRITES sprite, int16_t off_x, int16_t off_y, int16_t spd_x, int16_t spd_y);
+void obj_act(int16_t pos_x, int16_t pos_y, int16_t *spd_off_x, int16_t *spd_off_y);
 void obj_draw(int16_t spd_x, int16_t spd_y, uint8_t *hiwater);
 
 #endif // __OBJ_H__

src/sprites.h

@@ -22,6 +22,7 @@
 
 #include <stdint.h>
 
+#define SPR_NUM_START 0
 #define SHIP_OFF (8 + 4)
 
 enum SPRITES {