Cool idea. When you first shared your assets I thought it will be more arcady with player actually moving the moon there and back as a planetary-sized goalkeeper. I found ship doesn't have collisions until sent out but, on the other hand, one can send ships out and those will still properly collide even with asteroids that have appeared after that ship was sent out. Fancy.
Desired additions: Sound, music, button to get back to main menu, counter of asteroids ... and also asteroids appearing more often as time progresses and with truly random asteroid directions.
Ideas for later development: shop with upgrades. More moons. More dakka (aka quicker ships, quicker ship reload). Automatic guns on moons. Window clearing nukes...
Btw, what are "Platform" and "Rod" assets about?