Great game Dan!! Like the upgrade phase being more about exploring rather than just some button. Made it more interactive and fun.
A few bugs I noticed:
1. The mouse icon shakes/vibrated/glitches when the character is moving.
2. Triple shot is not that useful since when fired sideways; it does not spread but go in a single line. I think you already know this.
3. Some weird hitboxes when walking on thin paths
Apart from that, a really solid game. The art and music are also very well integrated into the game. Had lot of fun. Played like 8-9 waves before reading the rest :D
Kudos!!