Mission Objective: Your base, Capitol, has been attacked by intruders. You have to eliminate all of them to complete the mission.
Controls:
Left mouse to shoot. A,D, or left, right arrow keys to move. S, or down arrow keys to take cover. Spacebar to reload.
A context menu should be shown when right-clicking or, on touch devices, long-pressing in the game. This menu especially allows to play in full screen and control the volume.