Sure, here's an example of a simple Snake game implemented as a single HTML file using JavaScript. This game allows for multiple characters/snakes to be controlled on a smartphone using pictograms.
To use this game, simply copy and paste the code into a new HTML file, save it, and open the file in a web browser. The game will start automatically.
You can control the snakes using the arrow keys on your smartphone's keyboard or touch screen. The objective is to eat the red food dots to grow your snakes. Be careful not to collide with the walls or your own snakes, or it's game over!
Note that this is a simple implementation and can be expanded upon to add more features, levels, etc.