Sure! Here's a simple FPS shooter game implemented as a single HTML file using JavaScript, enclosed in script tags. The game assumes smartphone operation and uses pictograms for better visualization. Simply copy and paste the code into an HTML file, save it, and open it in a web browser to play the game.
This game creates a canvas element that covers the entire screen and allows you to control a blue square as the player using the arrow keys or 'WASD' keys. The objective is to shoot green squares using the mouse click, represented by red bullets. You earn points for hitting enemies, and the game ends when an enemy touches the player. The score is displayed in the top left corner of the screen.