Controls are W,A,S,D for movement, E for actions like opening ventilation hatches, disabling, etc., N is for night vision, mouse move for orbiting camera around player and mouse scroll for zooming in and out.
In the yard level, goal is to get through the yard undetected and enter the building.
In the first floor level, goal is to get to control room and disable laser grid on stairs leading to the upper floor.
After that return from control room to the stairs and go to the upper level.
In the second floor level, goal is to get through to the server room, disable main frame and escape through ventilation.