Wow I loved this game! I love the robo cop helmet and build craft. It feels like the upgrade tree will create good amount of replay. There was some decorative elements around the main treasure chest like a bucket and spatula which I wasn't sure if I could activate those or use them in some way. Once things really started getting busy I sometimes lost where my cursor was on screen, but maybe thats just part of the fun. I loved the bosses they added challenge! It would be cool if I started to face multiple of them at once. After a while I think there was no more upgrades, I would like if the game announced "Last Upgrade" to me to reinforce that. I would love to see a mode where the treasure chest was on a train track so instead of staying around the same place so I would have to walk along to defend it. I loved the chest changing as the enemy waves leveled up. The Music is good and put me in the zone. Really fun game.
Really glad that you really liked the game! And i agree with all of your feedback. It was my bad for the lack of upgrade variations as i have to limit the scope because of stuff so i kind of unintentionally neglect some obvious UX like Boss Incoming In.. or like you said Last Upgrade !
I was thinking about different boss behaviors and different enemy behaviors initially, but i took too long focusing on juice and feel of almost every upgrade modifiers. So i guess i'll frame this game as a Satisfaction Rain instead of real challenge, not that it's not challenging but i think for 70 - 80% of people the game is way too easy and it's my lack of design ability for that.
If there is going to be another jam, i will definitely create stuff with more variations in it, for sure.