Cheats
ZZT has a number of hidden cheat codes accessible by holding SHIFT and press ? to bring up a text-box in the upper-right corner.
Give all keys keys
Clears the flag 'flagname' -flagname
Sets the flag 'flagname' +flagname
Darken level +DARK
Un-darken level -DARK
Debug mode off -debug
Debug mode on +debug
Give 3 torches TORCHES
Give 5 ammo AMMO
Give 5 gems GEMS
Give 50 health HEALTH
Removes anything within 1 square ZAP
Be warned that setting/clearing flags and ZAP-ing may break a game world and render that savegame useless.
The ZAP command is particularly dangerous as it permanently removes anything within 1 square in each of the cardinal directions and replace it with an empty space. You can easily ZAP an object containing vital code that was disguised as scenery or a part of a wall.