Sure, here's an example of a simple game implemented as a single HTML file that meets your requirements. It's a game where you tap to make a character bounce from wall to wall, and the side you tap on is the side the character goes to. It uses pictograms for simplicity and assumes smartphone operation.
To play the game, you can open this code in a web browser on your smartphone. When you tap on the left half of the screen, the character will move towards the left wall. When you tap on the right half of the screen, the character will move towards the right wall. Similarly, tapping on the top or bottom half of the screen will make the character move towards the corresponding wall. The character will continuously bounce back and forth between the walls.