That was fun - I enjoyed it! Simple concept and well executed... it's really playable!
It does feel like you could expand on this quite a lot, but it's great as a starting concept and shows just how playable a more enhanced version would be.
Here's a few things that spring to mind that can be improved on:
- Have the bullets slower so it's more like you have to predict where the asteroid is going rather than a straight on direct hit
- Have asteroids split (like @ToreadorGames suggested). I mean, you could probably get away with just spawning two smaller asteroids half the size without accurately splitting the mesh.
- I didn't really feel much of a threat when playing the game, so adding some other objects at ground level might help to give extra threat in the game.
- I think this game would reach awesome status if you had two massive guns, one in each hand... imagine that, two massive cannons and you can double up the intensity of the asteroids & other threats!
Plus a few minor things. I feel you need to increase your shadow resolution in the quality settings, it's very low resolution and noticeable (don't worry, the quest hardware can take it!). The muzzle flash is quite distracting and it feel like it needs reducing. Also when pressing the settings & achievements menu buttons, they appeared behind me - I didn't see them at first.
Overall, a really fun and enjoyable game - a simple, clean idea done really well. Great job!