Great variety of upgrades! I liked the sound effects, the simple graphics reminded me of diep.io, and the track you managed to find on opengameart was brilliant, the doom-esque tune fit so well! I'm not sure how much I like the paying-for-upgrades-with-time mechanic, since you can't get time back it just feels like you're asking to play a little less of the game but get to have more fun. I think it would be interesting if killing enemies got time back, or something like that, in order to make the time-payments more risk/reward. Anyway, I did enjoy my time playing, nice entry :)