This doesn't feel playtested at all. I don't think it's even possible to lose at this. Enemies spawn from the exact same four spots every time so they're pitifully easy to kill before they can make any progress towards you, and they don't seem to speed up noticeably as the game progresses. You could play for hours and not be in any danger of dying whatsoever. Hell, if you stand in the right spot at the middle, you can just tap up-down-left-right in sequence while holding the fire button and play blind.