ZPC Cheats

Hold 'Ctrl' and type the following
tetsuo - Degreelessness Mode
ack - Oxygen
psion - Weapons
Level select:
Hold 'Alt' + 'Esc' when starting a new game.

Hold [Alt] + [Esc] and select the "New
Game" option.

Hold down the Alt and Escape keys while selecting the "New Game" option.

Hold [Ctrl] and type ack.

During gameplay hold down the CTRL key and type in one of the following codes

ACK - Health

PSION - Get Weapons

TETSUO - Invincibility