could be visual or something like a diagetic sound like ca-chunk or whoosh when you can do a particular ability again. I would say take a day and look at how twinstick shooters like binding of isaac or nuclear throne handle the hud for ability cooldowns. I envision something like risk of rain's cooldown counters. If you want something closer to home in bullet hells I would say check out the UI in xbla dodonpachi series. I thought the game felt just fine to play. Initially I felt that the dodge and the dash seemed to overlap in functionality, but I used the dash as a gap closer to hit gundams that run away.