Enter these codes at the password screen to play each level and start with nine lives:

Africa Level 1: 1431
Africa Level 2: 3731
Africa Level 3: 6937
Africa Level 4: 9701
Asia Level 1: 1123
Asia Level 2: 6831
Asia Level 3: 0377
Asia Level 4: 4267
Asia Level 5: 8099
Europe Level 1: 3163
Europe Level 2: 3204
Europe Level 3: 3198
Europe Level 4: 5941
North American Level 1: 2405
North American Level 2: 7069
North American Level 3: 5607
North American Level 4: 1525
North American Level 5: 9319
Nuclear warning, level 1: 1293
Nuclear warning, level 2: 4154
South East Asia Level: 1379
South East Asia Level: 7460
South East Asia Level: 8804
The capital is under attack, level 2: 0801
The capital is under attack, level 3: 5779
The capital is under attack, level 4: 1729