It's a little unclear about how the game works at first, but once you get a hang of it it's super addicting. It's really clever how the score is golden sand while asteroids hitting the walls or bombs exxploding makes other kinds of sand that are useless and make the time go down quicker.
The only real issue is how easy to knock around the player controller is, you basically never want to release the space button due to how hard it is to right yourself and you get thrown around by 2/3 shot types.
That doesn't seriously how fun the game is though, and I had a ton of fun! Great job!