Thank you so much for your detailed feedback!
I'm so happy to hear that you played it so long!
The music interruptions might have actually been because at the later rounds we pitch it up much more than usual (so that might mess with the buffer) I'll have to look into that.
The music is actually supposed to jump in pitch, it's just not supposed to cut out lol
It means you reached what I (personally) have playfully dubbed the "annihilation rounds"
Basically it's when the game decides that it's over and tries to kill you by spiking the difficulty a crazy amount each new round, increasing the enemy movement speed by a lot, to the point of being unbeatable. Signified with the audio queue of the music getting faster and higher pitch. but if i could go back, I would probably add a visual queue as well.
Any frame rate lag, was definitely unintentional though, if we had had more time to work on it prior to the deadline we probably would have focused on optimizing so that doesn't happen. A day before the submission ended I discovered a killer memory leak that was turning the game into a slideshow (literally 3 FPS) during the later rounds which thankfully was caught. But the game would no doubt benefit from further optimization!
I wholeheartedly agree, more mini-games are needed! If we end up continuing development with this game after the jam, more mini-games would absolutely be one of the first things to be added in.
As for the difficulty, maybe we should implement different difficulty modes.