Start game with solomisons.exe -console command line. Press ~ during game play to display the console window, then activate the following cheats by entering the corresponding codes. Press ~ or ESC to close the console window and resume game play:

CHEAT FUNCTION - CHEAT CODE
God mode - god
Flight mode - fly
Disable enemy AI - notarget
No clipping mode - noclip
Level select - map x<1-6>
Set game speed; default is 1 - 'timescale'
View credits - endgame