in Metro Siberia - Gravity can be a real nuisance when you’re trying get some ground clearance, but on the other hand it helps by keeping you from hitting your head against the ceiling. In this game you must find the right balance between working against gravity and using it to get back down in time. Try to stay airborne without hitting anything or it’s game over. Stay airborne for as long as you can without hitting anything. Press space to activate the booster. This will guide you aircraft up. Release it to go down again.