Pretty cool you made all this with just web technologies, you have my respect. I like the dark atmosphere and the sound effects are pretty nice.
Issues/Bugs:
- The movement feels pretty bad, perhaps it's the lack of a background to give you a reference frame. A bug I encountered is that when you get the movement speed upgrade, the extra movement speed only applies in the direction you're moving, I don't know whether this is intended or a bug but it feels pretty annoying.
- The difficulty ramps up really quickly, It went from barely spawning anything to spawning like 5 different enemies really quickly in just a minute.
- Carrying on from previous point, the game balance is pretty bad, I don't feel like im getting enough money from enemies but maybe that's just me.