Asteroid Invaders

Asteroid Invaders is a spin-off of the classic arcade game Asteroids.
It introduces 8 different play modes, one of which is the classic game, while the other seven alter your gameplay experience, like shooting for example.

The different mechanics aren't explained, however. This may seem like an oversight because I only have four hours left, but nooooo, this is a strategic and totally intentional decision, to challenge you to figure out the mechanic before you are utterly crushed by the asteroids!

Additionally, you can replay the same mode once you've played it once through the unlockable play-modes menu. Feel free to beat your scores, unlock all 8 modes, and deafen yourselves with the minigun mode's sound effects!
wait, was I supposed to reveal one of the modes just now? Ah, nevermind, they won't notice, I'm sure of it.

Good luck, and have fun!