Press F9 to pause the game. Hold HELP, Left Shift, and 1
(main keyboard). Let go of all three, and press F10 to
restart the game.
From now on the following keys are activated:
1-5 (main keyboard)-Warp to corresponding level
[F1]-[F4]-Warp to section 1-4 in current level
If you are almost dead, just use the F1-F4 keys
(depending on how far you are) for renewed strength.