When you rebound, you actually get an attack boost that scales with the more rebounds you chain together. Sorry that probably wasn't very obvious, but I plan to add more visual flare so players can actually tell when they're powered up, currently it just shows as a little number in the corner. You're meant to utilize those power-boosts to take down tougher enemies faster.
Thanks for the feedback, and for the asset link. I think I've heard of it before but I'd rather stick to the system I created as it allows me to have more low-level control of what can be done with bullets in the game. Plus, I wanted to challenge myself more as a programmer. (and I don't really wanna spend any money lol)