Successfully complete all objectives in the single mission dossiers. The following codes can now be enabled once you complete all objectives in the single mission dossiers

Invincibility:
Press Back and then press X(2), A, B, A during game play. A message will confirm correct code entry. Your first soldier will be invincible, but the remaining members of your platoon can still be harmed. Note: You cannot complete the game normally when this code is active, as maps and dossier items can no longer be unlocked.

Big Heads:
Press Back then press A, X, B, Y, A during game play. A message will confirm correct code entry.

Chicken Explosives:
Press Back then press X(2), Y, A, B during game play. A message will confirm correct code entry.

Paper Mode:
Press Back then press B, A, X, Y, A during game play. A message will confirm correct code entry. Characters will be two dimensional in this mode.

Slow Motion:
Press Back then and press Y(2), B, X, A during game play. A message will confirm correct code entry.

High Pitched Voices:
Press Back then press X, A, Y, B, X during game play. A message will confirm correct code entry.

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