Use the arrow keys to turn the snake. Don't touch your tail or the edge, or it's game over! Eat the food for points, and to get longer. Press the space bar for invincibility mode cheat, where you are a rainbow, and can't die! the lighting makes you go faster, so watch out!
Turning to face the opposite direction you are moving will instantly kill you, as you would be headed straight into your tail. This is not a bug, because if it DIDN'T kill you, you would be breaking the rules.