Rudimentary game! Refactored to make it possible for the game to restart
when the player is hit and asteroids spawn on a 1 second timer. Added
bgm music for flavour.
Refactored the unit tests so they don't check for a last position but
whether the game ends when the player collides with an asteroid
Small mistake in the tests, also leave DEBUG_MODE on for now because the
bounding boxes for the asteroids need to be fixed.