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Playstation 2 - Silent Scope 2 - Dark Silhouette cheats

Exchange a half of life for 5 sec:
Pause the gameplay and press Up, Up, Down, Down, Left, Right, Left, 
Right, X, Circle. The sound of a gun will confirm the code entry.

Exchange 5 sec for half of life:
Pause the gameplay and press Circle, X, Right, Left, Right, Left, 
Down, Down, Up, Up.The sound of a gun will confirm the code entry.

Increase credits to 3 in the options menu:
Continue the game at least 15 times

Increase credits to 4 in the options menu:
Continue the game at least 30 times

Increase credits to Infinite credits in the options menu:
Continue the game at least 100 times

Bonus lives
Lose all of the lives.  
Repeat a few times to increase the lives between 4-6.

Bonus time
Wait until the timer reaching zero and lose the game.
Repeat a few times to increase the time between 70-80.