This one is addictive, I ended up doing many "just one more run"s. My best was Wave 33, 93 kills. I wanted to reach 100 kills, and ironically at some point I think I faced a bug where I couldn't die then I took an heart, could die again and ended with exactly 100 kills, while before it happened I think I was at 98 or 99 so definitely not 100.
I had a lot of fun, the artwork has much personality, the game controls perfectly, all the speeds feel right and the difficulty ramps up at the appropriate pacing.
I think there could be a few additional sound feedbacks. Also the different health, fire rate and bullets are cool but one more thing which can also give each enemy more personality is if they shoot more than one bullet at once following a different pattern.
Thanks for sharing!