This was simple yet efficient, and pretty fun! Here are my points:
- Love the retro style, sprites and animations are cute;
- A small thing, but resetting character position for choosing upgrades felt like an unnecessary interruption;
- Enemies with more health should have something to let players know about their increased health;
- I kept getting more health, but never saw any indication of my health bar getting bigger;
- I've only played once so far so I couldn't check, is there a way to win?;
- Overheating mechanic felt satisfying without being too punitive.