Sure, here's a simple FPS zombie game implemented in a single HTML file using JavaScript and enclosed in script tags:
This is a basic implementation of an FPS zombie game using pixel-like rectangles as visual representations. The player is controlled using the WASD keys for movement and the mouse for aiming. Zombies spawn randomly on the game canvas and the player's objective is to avoid colliding with them. The game ends when the player collides with a zombie, triggering a game over message. Feel free to customize and enhance the game according to your requirements and preferences.