Yeah I also immediately noticed the flat attack cooldown duration upgrade and wanted to become a laser. It is a completely broken upgrade that is just objectively better than any other upgrade, especially after getting one damage upgrade that makes you oneshot everything, which makes upgrade choice rather uninteresting. However, I cannot deny the simple fun of abusing this to get overpowered and probably wouldn't have stuck around nearly as long if it were balanced. I really need to criticize the mixed pixel art resolutions though, it just looks so messy and unintentional. Consistency in art style is very important.
Congrats on making a game though!