Tyrian cheat codes:
Here's a list of all the codes and the ships you get to fly when
use them.

TECHNO = Experimental PQZ
STORMWIND = Stormwind - The Elemental
UNKNOWN = TX SilverCloud
ENEMY = Captured U-Fighter
WEIRD = Foodship Nine
STEALTH = Ninja Star
NORTSHIPZ = Nort-Ship Z

And for a change of pace use the last code, DESTRUCT. It will get
you into a weird real-time Scorched Earth type game called Destruct.

Press G when selecting Difficulty Level to enable the Impossible
difficulty level, then press } to enable the Suicide difficulty level.

Start the game with the command line
FILE0001 LOOT[Alt-254]
(press ALT and 254 on the keypad for the last character)

Invincibility:
Press [F2] + [F3] + [F6] during game play.

Level skip:
Press [F2] + [F6] + [F7] during game play.

Destruction mode:
Press [F2] + [F3] + [F5] during game play.
A message will confirm correct code entry.
Shields will be reduced to zero after one hit.

Extra money:
Press [F2] + [F3] + [F10] during game play.
Note: This code may be enabled in each level.

Christmas mode:
Set the system date to any day in December and load the game.

Super turbo mode:
Press [Backspace] +1 during game play.

Expert mode:
Type engage at the title screen. Note: This may only
be enabled in v2.0 and greater.

Easy mode:
Hold [Scroll Lock] and type engage at the title screen.
Note: This may only be enabled in v2.0 and greater.

Switch to story mode:
Press 2 during game play in arcade mode.