move obj movement into obj_act(), mask wrap of coordinates so items can be picked up after wrapping screens

src/game.c

             redraw = 1;
         }
 
-        pos_x += spd_x;
-        pos_y += spd_y;
+        pos_x = (pos_x + spd_x) & POS_MASK_BG;
+        pos_y = (pos_y + spd_y) & POS_MASK_BG;
         move_bkg(pos_x >> POS_SCALE_BG, pos_y >> POS_SCALE_BG);
 
         uint8_t hiwater = SPR_NUM_START;
             hiwater = ship_hiwater;
         }
 
-        obj_draw(spd_x, spd_y, &hiwater);
+        obj_draw(&hiwater);
         status(health >> HEALTH_SHIFT, power >> POWER_SHIFT, &hiwater);
 
         hide_sprites_range(hiwater, MAX_HARDWARE_SPRITES);

src/game.h

 #define SPEED_MAX_IDLE 16
 
 #define POS_SCALE_OBJS 5
+#define POS_MASK_OBJS 0x1FFF
+
 #define POS_SCALE_BG 6
+#define POS_MASK_BG 0x3FFF
 
 #define POWER_MAX 0x1FF
 #define POWER_SHIFT 1

src/main.c

         }
 
         uint8_t hiwater = SPR_NUM_START;
-        obj_draw(0, 0, &hiwater);
+        obj_draw(&hiwater);
         hide_sprites_range(hiwater, MAX_HARDWARE_SPRITES);
 
         vsync();

src/obj.c

 
 int16_t obj_act(int16_t *spd_off_x, int16_t *spd_off_y, int32_t *score) NONBANKED {
     int16_t damage = 0;
+    int16_t spd_x = *spd_off_x;
+    int16_t spd_y = *spd_off_y;
 
     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].off_x + objs[i].spd_x - spd_x) & POS_MASK_OBJS;
+        objs[i].off_y = (objs[i].off_y + objs[i].spd_y - spd_y) & POS_MASK_OBJS;
+
+        // only update travel time if we're actually moving
+        if ((objs[i].spd_x != 0) || (objs[i].spd_y != 0)) {
+            objs[i].travel += 1;
+        }
+
+        // remove objects that have traveled for too long
+        if (objs[i].travel >= MAX_TRAVEL) {
+            objs[i].active = 0;
+            continue;
+        }
+
+        // handle collission
         switch (objs[i].sprite) {
             case SPR_DARK:
                 if ((abs(objs[i].off_x) <= GRAVITY_RANGE) && (abs(objs[i].off_y) <= GRAVITY_RANGE)) {
     return damage;
 }
 
-void obj_draw(int16_t spd_x, int16_t spd_y, uint8_t *hiwater) NONBANKED {
+void obj_draw(uint8_t *hiwater) NONBANKED {
     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;
-        objs[i].off_y += objs[i].spd_y - spd_y;
-
-        // only update travel time if we're actually moving
-        if ((objs[i].spd_x != 0) || (objs[i].spd_y != 0)) {
-            objs[i].travel += 1;
-        }
-
-        // remove objects that have traveled for too long
-        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, 0, hiwater);
     }
 }

src/obj.h

 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);
 int16_t obj_act(int16_t *spd_off_x, int16_t *spd_off_y, int32_t *score);
-void obj_draw(int16_t spd_x, int16_t spd_y, uint8_t *hiwater);
+void obj_draw(uint8_t *hiwater);
 
 #endif // __OBJ_H__