Sure! Here's a simple game using JavaScript that can be implemented as a single HTML file. It can be played on smartphones and uses pictograms for visuals.
Swim in a River Game
Tap the screen to move the player across the river!
You can save this code as an HTML file and open it in a web browser on your smartphone to play the game. The player, represented by a swimming pictogram, can be moved horizontally across the river by tapping or dragging on the screen.