Sure, here's an example of an HTML file containing a simple game written in JavaScript, which can be played on a smartphone:
This example sets up a simple game where the player controls a square using right and left arrow keys on their smartphone screen. The square moves horizontally within the canvas. The code utilizes the `<canvas>` element and its associated JavaScript API to draw and manipulate shapes on the screen. The game loop continuously clears the canvas and redraws the player's position based on the input provided.