Below is an example of a simple 3D hopper game implemented as a single HTML file using JavaScript. The game is designed for smartphone operation and uses pictograms.
In this 3D hopper game about Grimace, you control a character represented by a white square (for simplicity, since pictograms may not be readily available). The goal is to make the character hop over obstacles represented by red and green squares. Touching the obstacles resets the jump.
To play the game on a smartphone, save the above code as an HTML file and open it in a mobile browser. It will automatically start the game, and you can make the character jump by tapping the screen.