Thanks for the feedback, really appreciated ^.^
Yup, I wanted to implement some camera shake, and other effects, but I had to give up on those due to the time constraints :/ This is my first time coding a game in HTML5/JavaScript so a lot of my time was spent figuring things out, which meant less time to work on nice-to-have features. So i had to settle for some mediocre bleep-bloops as feedback ><
As for the reward for good play... that's a good question! I'm not entirely sure what would work here. Maybe there could be a threshold on the meter, and if you are above it when the level/difficulty changes, you get some sort of stat bonus? Could be simply more damage, more resistances, maybe an extra life of sorts? Or a powerup that allows you to temporarily slow down time without taking damage?
I might continue working on this next weekend. Adding some more JUICE~