To use the codes type them in at the console.
 Press the ~ key to bring up the console.
 
 impulse 11      Invulnerability
 ode to jack     Kill all enemies
 impulse 10      Big magic attack
 fly             Fly mode toggle (press jump key to fly)
 dir maps        List available levels
 map x           (Where x is the level name) Level warp
 noclip          No clipping mode toggle
 impulse 43      Suicide
 impulse 69      Another suicide