Nice idea and the game is nicely done. I think the game stops spawning enemies after a while (or I am doing something wrong) so it would be more fun to keep them spawning and let players compete for scores. I also noticed that after shooting, I keep orbiting the mouse pointer and I can use that to move the player sideways till I am in a good position to shoot again (I don't know if that's intentional or not). I like the effect of changing the music tempo during holding down the mouse button, it adds a nice feeling to the game. Overall, it is really fun, good work.

Good game but if we wanted to enter semantics technically  a 1-bit game would consit entirely of just two colors. But if I wasn't a nitpicky know-it-all I'd say I really like how good it feels to hold a charge and blast forward. 9/10