This was a fun fast-paced survival game! I really enjoyed how hard mode added increased enemy variety, it felt rewarding to try out the different difficulty levels. I also like the variety in the upgrades, so the player can explore different builds.
I do feel like it was more difficult than I expected to gain money in hard mode. I think especially with the faster and higher-damaging enemies, I felt like I had much less time to get any upgrades before my health got low.
Additionally, I think it would be nice if there was a visual indicator of where enemies will spawn in, since enemies can spawn even when you are close to a spawn point.
Overall, I liked playing this game, and it had some good replayability.