On the title screen, type "LISTEN TO THE WHALES" for invincibility. The life meter will still decrease, but you won't die. If you fall in a hole you will still die!
While your in the taxi, type "JIMMY HENDRIX" for infinite energy.
First, go right, collect the gun, then run to the right and jump over the first lift. Keep running to the next lift, go up three times and walk onto the lift that is waiting when you arrive. Go up, then left and collect the gun. Now go right to the next lift and down once. Go onto the next lift, and go up as far as you can see. Walk right, off the lift and run right to the next lift, picking up the object on the way. Go up on the lift, run right and go down three times on the next one that you come to. Run left, go down on the lift and run left again to collect the object. Run right to the first lift and go up, then go to the next lift and go up twice. Run right and go up on the lift once, then run and jump right. Collect the heart, run right,drop down through the hole and run to the exit.