In this game, you play as sniper. Your task is to eliminate all targets in area. Keep in mind, that there are two factors, that determinates your bullet once it is shot - wind and distance. Also be aware of misshooting. You don't want to alert hostiles, do you?
Move your scope with arrow keys, steady your aim by holding M, shoot with N. If you somehow get stuck, press R. If you for some reason, I would really wonder why, want to exit game, press Escape. It is pointless tip, I know.
Have fun playing this!