Challenging & fun! Not bad for a gamejam project.
I wouldn't consider changing the number of hearts to be "changing difficulty" though. Kinda wish there was a pause button to change difficulty, or controls, in the menu instead of refreshing my browser.
I'm glad you guys put in checkpoints cuz this game is arguably harder than the classic Megaman games. The controls are very tight & responsive though, which is perfect for this type of Megaman-style gameplay.
The level designing & enemy placements was ok, however the very first level before the very first checkpoint was a little bit TOO challenging in my opinion for players who are just starting out. It would've been better as a 2nd or 3rd level. Not quite sure what the coins & treasure is for, but hopefully it'll be to purchase that SHOTGUN you mentioned! That'd be $&%#ing sweet! Also, WHY IS IT RAINING DYNAMITE after the first checkpoint?!
I also seem to do more jumping than actual shooting until the boss fight.
The boss fight was awesome btw! Prob my fav part of this game.
The audio & visual feedback of shooting and killing stuff is very satisfying. The music choice was very appropriate for this 8-bit horror theme.
Good job :)