Sure! Here's an example of a simple top-down open world space RPG game implemented in a single HTML file using JavaScript:
In this example, the game consists of a simple rectangle representing the player, which can be controlled using touch controls on a smartphone. The player can move in four directions (up, down, left, right) with a fixed speed (5 pixels per frame). The game loop updates the game state and redraws the player on the canvas, while the touch event handlers capture the player's input.