Type in the codes in CAPITAL letters, an you find 
 new option in the pause menu [= ESC].
 
 Code       Result
 -----------------
 CHEATSEQ - Activate cheat mode
 HHROQTAT - Weapons
 TERHSRER - Next level
 CCHASERQ - Repairs
 HTARSREC - Items
 HERHSORE - Win level
 QHEROEST - Win all levels