I really like the retro-like artistical style of this game and the idea. But what I think is especially important for these kind of games is responsiveness in the form of audio, screenshake, animations, etc. Polish takes time, but it's always worth leaving time for (and often something that's skipped in the time pressure of game jams). I like that the upgrades lean into the countdown timer, both because it's an interesting dynamic that makes for multiple strategies but also because it fits the theme so well. I do however think there's some balancing that's needed there (which don't get me wrong is very difficult to get right for such a short jam). I like the direction of this game, and I hope my little write up could help share my thoughts on how this project might be expanded should you choose to do so. Overall well done!