Fix misc math bugs

game/game_collision.c

@@ -9,29 +9,50 @@ bool game_collision_is_occlusive(sys_maptile tile) {
     return false;
 }
 
+// c's modulus can produce a negative result. don't allow that!
+#define modulus(x, mod) ((x) % (mod) + (mod)) % (mod)
+#define round_down(x, incr) (x) - modulus(x, incr)
+#define round_up(x, incr) round_down((x) + (incr) - 1, incr)
+
 bool game_collision_can_move(game_bbox body, sys_i32 dx, sys_i32 dy) {
+    // First: place the body in space.
+    // Align its top-left corner to the pixel boundary
     sys_i32 x = body.x + dx;
     sys_i32 y = body.y + dy;
 
-    // the player can never leave the map
+    // this is extremely similar to the logic in move_to_contact
-    if (x < 0) { return false; }
+    // but has different rounding behavior
-    if (y < 0) { return false; }
+    // (because a body at a fractional position must not actually collide
-    if (x + body.w > map_game_map.width * TILE_SZ_MICROPIXEL) { 
+    //  with fractional pixels)
+    sys_i32 body_x0 = round_down(x, PIXEL_SZ_MICROPIXEL);
+    sys_i32 body_y0 = round_down(y, PIXEL_SZ_MICROPIXEL);
+    sys_i32 body_x1 = body_x0 + body.w;
+    sys_i32 body_y1 = body_y0 + body.h;
+
+    sys_i32 tile_x0 = round_down(body_x0, TILE_SZ_MICROPIXEL);
+    sys_i32 tile_y0 = round_down(body_y0, TILE_SZ_MICROPIXEL);
+    sys_i32 tile_x1 = round_up(body_x1, TILE_SZ_MICROPIXEL);
+    sys_i32 tile_y1 = round_up(body_y1, TILE_SZ_MICROPIXEL);
+
+    // now convert to tile coords instead of pixels
+    tile_x0 /= TILE_SZ_MICROPIXEL;
+    tile_y0 /= TILE_SZ_MICROPIXEL;
+    tile_x1 /= TILE_SZ_MICROPIXEL;
+    tile_y1 /= TILE_SZ_MICROPIXEL;
+
+    for (sys_i32 y = tile_y0; y < tile_y1; y++) {
+        for (sys_i32 x = tile_x0; x < tile_x1; x++) {
+            bool invalid;
+            sys_maptile tile = sys_map_get(map_game_map, x, y, &invalid);
+            if (invalid || game_collision_is_occlusive(tile)) {
                 return false;
             }
-    if (y + body.h > map_game_map.height * TILE_SZ_MICROPIXEL) { 
+        }
-        return false; 
     }
 
-    // TODO: Collide with blocks
-    // If two collides with a block, check if one collides with it.
-    // The collision only matters if one doesn't.
     return true;
 }
 
-#define round_down(x, incr) (x) - (x) % (incr)
-#define round_up(x, incr) round_down((x) + (incr) - 1, incr)
-
 game_collision game_collision_move_to_contact(
     game_bbox* body, sys_i32 total_dx, sys_i32 total_dy
 ) {

game/game_collision.h

@@ -5,6 +5,7 @@
 #include "sys/sys.h"
 
 #define TILE_SZ_MICROPIXEL 0x800
+#define PIXEL_SZ_MICROPIXEL 0x100
 
 typedef struct {
     sys_i32 x;
@@ -24,4 +25,4 @@ bool game_collision_is_occlusive(sys_maptile tile);
 bool game_collision_can_move(game_bbox body, sys_i32 dx, sys_i32 dy);
 game_collision game_collision_move_to_contact(game_bbox* body, sys_i32 x, sys_i32 y);
 
-#endif
+#endif  // GAME_COLLISION_H

game/game_player.c

@@ -5,12 +5,15 @@
 #include "game.h"
 #include "sys/sys.h"
 
+#define GAME_PLAYER_ORIGIN_X 4
+#define GAME_PLAYER_ORIGIN_Y 4
+
 game_bbox game_player_bbox = {
     .x=0x9000,
     // .y=0x5800,
     .y=0x0000,
-    .w=0x1000,
+    .w=0x0800,
-    .h=0x1000,
+    .h=0x0c00,
 };
 bool game_player_grounded = false;
 sys_i32 game_player_jump_frames = 0;
@@ -44,7 +47,9 @@ void game_player_update() {
     if (collision.collided_x) { game_player_dx = 0; }
     if (collision.collided_y) { game_player_dy = 0; }
 
-    game_player_grounded = !game_collision_can_move(game_player_bbox, 0, 1);
+    game_player_grounded = !game_collision_can_move(
+        game_player_bbox, 0, PIXEL_SZ_MICROPIXEL
+    );
 
     {
         sys_i32 fric_numerator = game_player_grounded ? 0x70 : 0x7f;
@@ -63,8 +68,11 @@ void game_player_update() {
     
         // allow this if grounded or if it's not a change of direction
         if (
+            /*
             game_player_grounded || 
             (sys_sgn_i32(wanted_dx) == sys_sgn_i32(game_player_dx))
+            */
+           true
         ) {
             game_player_dx = wanted_dx;
         } else {
@@ -74,19 +82,20 @@ void game_player_update() {
     }
 
     if (game_player_grounded || game_player_coyote_frames > 0) {
-        if (sys_btn(DEVICE_BUTTON_U)) { 
+        if (sys_btnp(DEVICE_BUTTON_U, false)) { 
             game_player_dy = -0x300; 
             game_player_jump_frames = 15;
             game_player_grounded = false;
         } 
     }
 
+    if (game_player_dx < 0) { game_player_faceleft = true; }
+    if (game_player_dx > 0) { game_player_faceleft = false; }
+
     bool wants_to_go_higher = false;
     if (game_player_grounded) {
         game_player_coyote_frames = 5;  
         if (game_player_dy > 0) { game_player_dy = 0; }
-        if (game_player_dx < 0) { game_player_faceleft = true; }
-        if (game_player_dx > 0) { game_player_faceleft = false; }
         if (sys_abs_i32(game_player_dx) < 0x20) { game_player_dx = 0; }
     }
     else {
@@ -108,7 +117,7 @@ void game_player_update() {
         } else {
             game_player_anim_transition(GAME_PLAYER_ANIM_WALKING);
             game_player_anim_add_progress(
-                sys_min_i32(sys_abs_i32(game_player_dx) / 0x10, 0x8)
+                sys_min_i32(sys_abs_i32(game_player_dx) / 0x10, 0x20)
             );
         }
     } else {
@@ -138,8 +147,8 @@ void game_player_draw() {
     sys_sprite_draw_ext(
         spr_game_player,
         game_player_image,
-        game_player_bbox.x / 0x100, 
+        game_player_bbox.x / 0x100 - GAME_PLAYER_ORIGIN_X, 
-        game_player_bbox.y / 0x100, 
+        game_player_bbox.y / 0x100 - GAME_PLAYER_ORIGIN_Y, 
         2, 2, 
         game_player_faceleft, false
     );

sys/sys_graphics.c

@@ -295,6 +295,24 @@ void sys_map_draw(
     }
 }
 
+sys_maptile sys_map_get(
+    sys_map map,
+    sys_i32 tile_x, sys_i32 tile_y,
+    bool* flag_invalid
+) {
+    if (flag_invalid != NULL) { *flag_invalid = false; }
+
+    if (
+        tile_x < 0 || tile_y < 0 ||
+        tile_x >= map.width || tile_y >= map.height
+    ) {
+        if (flag_invalid != NULL) { *flag_invalid = true; }
+        return 255;
+    }
+
+    return map.tiles[tile_x + map.width * tile_y];
+}
+
 // == internal primitives ==
 void sys_pixel_internal_set(sys_i32 x, sys_i32 y, sys_color c) {
     sys_color realc = sys_dpal[c];

sys/sys_graphics.h

@@ -179,4 +179,16 @@ void sys_map_draw(
     // TODO: Layers?
 );
 
+/**
+ * Get a single map tile, putting whether the coords were invalid into
+ * flag_invalid.
+ * 
+ * (flag_invalid may be null)
+ */
+sys_maptile sys_map_get(
+    sys_map map,
+    sys_i32 tile_x, sys_i32 tile_y,
+    bool* flag_invalid
+);
+
 #endif // CROCPARTY_SYS_GRAPHICS_H

sys/sys_input.c

@@ -25,9 +25,10 @@ bool sys_btn(DeviceButton button) {
     return sys_input_down_frames[button] >= 1;
 }
 
-bool sys_btnp(DeviceButton button) {
+bool sys_btnp(DeviceButton button, bool repeat) {
     if (button >= DEVICE_BUTTON_N) { return false; }
     if (sys_input_down_frames[button] == 1) { return true; }
+    if (!repeat) { return false; }
     // 31 and every 8 frames after that
     if (sys_input_down_frames[button] >= 31 && (sys_input_down_frames[button] - 31) % 8 == 0) { 
         return true; 

sys/sys_input.h

@@ -26,8 +26,9 @@ bool sys_btn(DeviceButton button);
 /**
  * Return whether a button was just pressed.
  * 
- * Repeats after 30 frames, returning true every 8 frames after that.
+ * If `repeat`, then this repeats after 30 frames, returning true every 8 
+ * frames after that.
  */
-bool sys_btnp(DeviceButton button);
+bool sys_btnp(DeviceButton button, bool repeat);
 
 #endif // SYS_INPUT_H