Sure, here's an example of a bullet hell game implemented as a single HTML file using JavaScript:
In this game, you control a circle sprite (player) using on-screen buttons for up, down, left, and right movements. The player's position is updated based on the button presses, and the game canvas is continuously updated with the player's new position. The game loop runs using `requestAnimationFrame`. The game canvas has a black background, and the player is drawn as a white circle using the `drawPlayer` function.