sw, sh = 8, 8
function is_colliding(a, b)
  ax1, bx1 = a.pos.x, b.pos.x
  ax2, bx2 = ax1 + sw, bx1 + sw
  ay1, by1 = a.pos.y, b.pos.y
  ay2, by2 = ay1 + sh, by1 + sh
  return (ax1 < bx2 and ax2 > bx1
        and ay1 < by2 and ay2 > by1)
end

function handle_collision(a, b)
--   if b.typ == types.enemy then
--     --print(b.id,100,100)
--   end
end

function run_collisions()
  collidable = filter(World, function (e) return e.collision end)
  for _ai, a in ipairs(collidable) do
    for _bi, b in ipairs(collidable) do
      if a.id == b.id then
        goto continue
      end
      if is_colliding(a, b) then
        handle_collision(a, b)
      end
      ::continue::
    end
  end
end