Sure, here's an example of a simple Attack on Titan game implemented as a single HTML file using JavaScript:
In this game, you control the blue player box at the bottom of the screen using left and right arrow keys on your smartphone keyboard. Pressing the spacebar (or a mock spacebar on your smartphone) triggers an attack on the red titan box on the top right corner. The titan briefly changes to green color to indicate a successful attack.
Please note that this is a very basic example just to demonstrate the concepts and functionalities of the game. For a complete and more immersive game, you would need additional features, graphics, animations, and gameplay mechanics.