I gave the build a go; you've definitely got the speed aspect down already with the particles and the striped environment.
Some random thoughts/feedback I thought of while playing, forgive me if it's not the direction you're thinking towards:
- Something that might be cool to add is a barrel-roll with invincible frames (with a cooldown of course) for more easily avoiding enemy projectiles every once in a while.
- Right now you're currently holding down the attack button (left click) a lot, and that this doesn't necessarily change even while you accrue powerups; I wonder if it might feel more satisfying to have powerful powerups that fire with say, a right click. Waiting for the sniper to charge and the unleashing his shot with a right click would feel pretty good.
- Perhaps rather than (or maybe in addition to!) a health system, powerups would be destroyed, leaving you weaker as you got hit.
- You mentioned Binding of Issac, it'd be intriguing to create a sort of roguelike based on a starfox sort of game, based on taking different paths via forked in each level.
Looking forward to where you're going to take it.