Bonus levels
Successfully complete the game with the indicated number of "Gold" ranks to unlock the corresponding bonus level. To access them, press [X] at the level selection screen to display the "Lost Levels" level selection screen.
Ancient Rome - Praetorian Camp: 3 "Gold" ranks
Ancient Rome - The Forum Romanum: 5 "Gold" ranks
Ancient Rome - The Forum of Trajan: 7 "Gold" ranks
Ancient Rome - Addressing the Senate: 9 "Gold" ranks
Ancient Rome - Caesar's Sanctum: 12 "Gold" ranks
Feudal China - The Silk Road: 15 "Gold" ranks
Feudal China - The Gate of Supreme Harmony: 18 "Gold" ranks
Legendary Atlantis - The Steam Tower: 22 "Gold" ranks
Legendary Atlantis - The Geothermal Tunnels: 24 "Gold" ranks
Legendary Atlantis - The Corridors of Power: 26 "Gold" ranks
The Gallery: 31 "Gold" ranks
All weapons
Successfully complete the game with 33 "Gold" ranks.
Glitch: Stuck in corner
On the second level, enter the room with the shotgun in it and two cases of ammunition. Once you enter through the door, look to the left. You should see a pole a short distance away from you. Go to it and go to the other side. Note: Do not go behind; go in front of it. Then, look towards the corner. You should see a shadow. Jump into it, then look towards the pole and back up slightly. You should now be stuck. The only way you can get out is to wait a short time. You should be able see under the level for a moment. You can now walk around.