Mad Combat Marines is a first-person shooter game where players take on the role of a soldier fighting against an enemy force in a nearly destroyed city.
The player's objective is to shoot and eliminate as many enemies as possible in each level, while collecting power-ups and health packs to aid in the task.
The game runs in the browser without download or registration, allowing players to simply click and start playing. The core mechanic involves moving through the ruined streets, using cover to avoid taking damage, and engaging in combat with the enemy.