Sure! Here's a simple game where a cat chases the player and the player needs to run away. The game will be implemented as a single HTML file with JavaScript code enclosed in script tags.
In this game, you control the player using the arrow keys on your smartphone. The blue square represents the player, and the red square represents the cat. The cat will chase the player, and if it touches the player, the player dies and the game ends. You can run this HTML file in a web browser on your smartphone, and the game will be playable.