For a "Scorched Earth" clone, type "destruct" at the main menu. Press F1 when the game begins for help.
If your system clock's month is set to December then the game will ask you at startup if you want to play Christmas Tyrian.
When you start a game, press F2, F3 and F10. You'll have to repeat this code on each level.
For a harder game, press G when you select the difficulty.
While playing, press F2+F3+F6 for invincibility.
While playing, press F2+F6+F7 to skip to the next level.
During a game press F2 + F3 + F5 at the same time to play the stage with no armor. Repeat for each level.
For an even greater challenge, press } on the difficulty selection screen.
For an awesome ship, type any of these at the main menu screen:
Type ENGAGE at the title screen. This codes works on versions 2.0 and later. For an easier version, hold the SCROLL LOCK button while typing it in.
For the fastest speed possible, press Backspace and '1' at the same time.