Level Codes:

 2: 353828   6: 847464   10: 193831   14: 103992
 3: 108383   7: 737373   11: 090921   15: 998112
 4: 370101   8: 928112   12: 309383   16: 125332
 5: 982822   9: 267364   13: 101221   17: 091233

 Cheat Codes

 Code     Effect

 000000 = ?
 736353 = Start with 50000 credits.
 098654 = Start with 10 lives.
 378829 = Start with 50 keys.
 243433 = Skip levels by pressing N during play.