Fix misc math bugs

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