Seek and destroy the enemies within the city using your sniper rifle.
HOLD down the mouse button to zoom in. RELEASE the button to fire the weapon. Try to aim for the head for maximum points. There are 3 levels (or 'zones'). Look out for health power-ups to maximize your time in a zone. Hit SPACEBAR to escape a zone when you're nearly out of health. The longer you manage to stay in a zone, the more points you will score.
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.