This is really well made and polished! Can't believe you've done this within just a week! I like the graphics, the gameplay is super satisfying, the sounda although a bit quiet (I've already maxed it out but still quiet) is really nice. Ironically, the worst weapon is the shotgun and the best ranged weapon is actually the club. Not sure why but that feels funny as hell. In casual two club throws can kill three enemies with ease and that yields another club. Infinite energy!!!
For some minor nitpicks I would say the upgrade system doesn't feel as impactful as one would think, and by stacking up at least 7-8 movement upgrades that I finally felt I was moving faster. I would also say the weapon variation is a bit lacking, and it felt repetitive quite quickly after a while of gameplay (I know that's just a week, but hey let me nitpick. Also please give me the uzi).
Anyway, this is really really well done! Good job!