Play a game of pong (or some other sports-like thing) … but you’re snakes that grow over time.
The usual rules of snake apply: your body grows behind you, and you can’t touch it.
Snakes move over a grid, the ball does not.
To simplify the game, you automatically move forward and the grid shows arrows. When you tap the screen, you simply rotate left/right in the direction of your current arrow.
You also shrink automatically?
So you can’t constantly defend your own goal, you need to get out of your way to eat something extra and stay at a good size.