Start the game with the hl.exe -dev -console -game
action command line. This enables the console window. You
can enter the original Half-Life missions with Action
Half-Life's weapons and models. The scientists, aliens, and
Barneys are the same and are fun to kill. When you enter the single
player mission, display the console window and type sv_cheats
1 to enable cheat mode. Then, type /god for God mode,
/impulse 101 for all weapons, /noclip to fly around
through everything, and /notarget for everything to ignore
you. Note: The game will eventually glitch.