A Box of Space Snakes
You are a space snake. You live in a box in space. If you are pushed out of the box, you will explode. If you use your gun to push other snakes out of the box, your tail will grow and you will score points. The longer your tail is, the bigger your scores will be, but you will also be an easier target.
My current high score: 258510
The trick, I think, is knowing when to cut your tail off. And also being able to quickly disentangle yourself from it. As in life, so too in games, it seems. When you are reincarnated as a space snake, you will thank me.