2D Space Shooter thingy - (Not) my first game

Your objective is to destroy all the incoming asteroids. They come in waves, each wave being separated from the next by a few seconds. You start the game with 3 Hit Points (HP), every collision with an asteroid will take you 1 HP (no matter its size), and if your HP reaches 0 its game over. Destroying asteroids will earn you points, and youll lose some for each asteroids that reaches the bottom of the screen (it wont affect your HP). Each time you survive 5 waves in a row without taking a single...