Was pretty entertaining. I beat it on 28 because I didn't understand the castle objective until I was already maxed out lol.
Initially I also thought the price of an upgrade was what my stat currently was - ex: I thought I had 25 strength, but it cost 25. So I was a little confused on how to purchase upgrades at first.
Overall good job! In the future maybe some more enemy variety, bullet patterns, and some different upgrades - projectile amount, size, etc.