Sure, here's an example of a simple Doom-like shooter game implemented as a single HTML file, enclosed in script tags, using JavaScript. Please note that this is just a basic example showcasing the game mechanics and it doesn't include the actual Doom graphics or extensive features. You can customize and expand upon it as per your requirements.
This HTML file will display a canvas with the player represented by a pictogram and enemies represented by another pictogram. The player can move using the arrow keys and shoot using the spacebar. The goal is to shoot and eliminate as many enemies as possible.
Feel free to enhance the graphics, gameplay mechanics, and add additional features to make it a more complete and enjoyable game.