Enter these on the password menu:

 MAYDAY- level 2  
 VICTORY- level 3  
 CHALLENGER- level 4  
 AZIMUTH- level 5  
 REVEALED- level 6  
 STONEAGE- level 7  
 WARFARE-level  8  
 OXYGEN- level  9  
 SKYHIGH-level  10  
 SUNSHINE- level 11  
 BLOWUP- level 12  
 NEUFTROIS- level 13  
 BARACUDA- level 14  
 GIVEAWAY- level 15  
 WATERFALL- level 16  
 SEVENTEEN- level 17  
 NEARTHEEND- level 18  
 Y2K- level 19