Hyperspace Invaders II: Pixel Edition is a hardcore, uncompromising vertical scrolling bullet hell/invader hell shooter (shmup) that doubles as a techno-based lightsynth, triggering bursts of funky ...

The game never indicates it, but it's possible to adjust the SFX and Music volume settings in the middle of the gameplay, without needing to go back to the option screen, or even having to pause.