Snake supports touch, gamepad, and keyboard controls.
The objective of the game is to eat as many apples as you can without crashing into yourself or any of the discarded apple cores. The snake can only be steered up, down, left, or right.
When using touch input, you can swipe up, down, left, or right anywhere on screen to steer the snake. In addition to using standard discrete swiping gestures, you can also place your finger or thumb anywhere on the screen and then drag up, down, left, or right but without lifting your finger off the screen at the end. Once you drag far enough it will be registered as an input for the direction you dragged and since your finger is still touching the screen, you can then continue to drag again up, down left, or right to input your next steering command. In this way you can steer through multiple twists and turns without needing to lift your finger between each one. Whichever method you use is up to you - don't be afraid to experiment!
Aside if you're interested: Why doesn't Snake have an on-screen d-pad controller?
Gamepad input is relatively straightforward: you can control the snake by using either the d-pad or the left thumbstick and the snake will steer in the indicated direction. You can either tap the d-pad buttons or flick the stick in the desired direction or press and hold them - whichever you prefer.
Keyboard input supports several mappings for each of the four directions:
UP: Use the UP arrow, the W key, or the 8 on the keypad
DOWN: Use the DOWN arrow, the S key, or the 2 on the keypad
LEFT: Use the LEFT arrow, the A key, or 4 on the keypad
RIGHT: Use the RIGHT arrow, the D key, or 6 on the keypad