attempt to optimize collision

it's actually worse

vacuum_gambit.p8

@@ -567,12 +567,8 @@ end
 
 function hurtbox(ship)
  local h = ship.hurt
- return {
-  x=ship.x + h.x_off,
-  y=ship.y + h.y_off,
-  width=h.width,
-  height=h.height
- }
+ local x1,y1 = ship.x + h.x_off, ship.y+h.y_off
+ return {x1, y1, x1+h.width, y1+h.height}
 end
 
 function ship_m:maybe_shoot(gun)
@@ -1356,14 +1352,14 @@ end
 -->8
 -- collisions
 
--- box: x, y, width, height
-
-function collides(box1, box2)
-	return not (
-	  box1.x>box2.x+box2.width
-	  or box1.y>box2.y+box2.height
-	  or box1.x+box1.width<box2.x
-	  or box1.y+box1.height<box2.y)
+-- box: x1, y1, x2, y2
+function collides(b1, b2)
+ -- x1, y1, x2, y2
+	return 
+	  b1[1]<=b2[3]
+	  and b1[2]<=b2[4]
+	  and b1[3]>=b2[1]
+	  and b1[4]>=b2[2]
 end
 
 collider = mknew{
@@ -1384,10 +1380,10 @@ collider = mknew{
 }
 
 function collider_indexes(box)
- local ret = {}
- for x = box.x\8, (box.x+box.width)\8 do
-  for y = box.y\8, (box.y+box.height)\8 do
-   add(ret, x+256*y)
+ local ret, ylo, yhi = {}, box[2]\8, box[4]\8
+ for x = box[1]\8, box[3]\8 do
+  for y = ylo, yhi do
+   add(ret, x+(y<<8))
   end
  end
  return ret