Sure, here's a simple cube game implemented as a single HTML file using JavaScript:
In this game, the cube moves based on the user's device motion. The cube starts at the top-left corner and using the device's accelerometer, it adjusts its position based on the device's movement in the X and Y axes. The cube will move dynamically as you tilt your smartphone. The cube is represented as a red square in this example.
Note that this implementation assumes that the device supports the `mousemove` event, which is commonly available on most modern smartphones. Make sure to open the HTML file on a smartphone to play the game.