This is a simple "Doom" game implemented as a single HTML file using JavaScript. The game involves a player (red rectangle) moving around on the screen using either keyboard arrow keys or touch controls on a smartphone. The objective is to avoid collision with monsters (blue rectangles) moving across the screen. The score increases by 1 every time the player avoids a monster, and a new monster is created every 100 points. The game ends when the player collides with a monster, and the "Game Over" message is displayed on the screen.