The serpent must not escape. You can play in:
How to play on the iPhone / iPad?
Swipe to change the direction
How to play on Apple Watch?
Move the "Digital Crown" wheel to change the direction.
Can send the score to Ranking. Also from Apple Watch!
To submit the Apple Watch score to the ranking:
1- The iPhone and Apple Watch must be linked.
2- Play with the Apple Watch and before sending the score, open the app on the iPhone. When you press "Send Score" from Apple Watch, a screen on the iPhone with the score will be ready to send.
Now you can know if you are the best on the Apple Watch!