You are being trained to advance in enemy field, and you have to test your shooting skills. Many game modes are available: fulfill missions, training camp, against the clock, etc.
Space bar to open the gates and pass to the next level. Move the mouse to aim, click to shoot. Use the V key to activate the night vision and the Q key to switch weapons. Arrow key down to go back to main menu. R key to reload the weapon, F for other special actions.