Sure! Here's a simple fighting game implemented as a single HTML file using JavaScript, enclosed in script tags:
This small game sets up a canvas element where the players (represented by blue and red squares) can move horizontally. If the two players collide, a game over message is displayed, and the game is reset. The game loop is implemented using `requestAnimationFrame` to continuously update and draw the game on the canvas. It can be played directly in a browser, including on a smartphone.