Half Life

Invincibility:
Go to the Cheat Code screen in the Options menu and enter the following cheat to unlock Invincibility: LEFT, SQUARE, UP, TRIANGLE, RIGHT, CIRCLE, DOWN, X. Press START to confirm code. If done correctly, the code will appear in the box to the right.

Unlimited Ammo:
Go to the Cheat Code screen in the Options menu and enter the following cheat to unlock Unlimited Ammunition: DOWN, X, LEFT, CIRCLE, DOWN, X, LEFT, CIRCLE. Press START to confirm code. If done correctly, the code will appear in the box to the right.

Unlock Alien Mode:
Go to the Cheat Code screen in the Options menu and enter the following cheat to unlock Alien Mode: UP, TRIANGLE, UP, TRIANGLE, UP, TRIANGLE, UP, TRIANGLE. Press START to confirm code. If done correctly, the code will appear in the box to the right.

Unlock Invisibility:
Go to the Cheat Code screen in the Options menu and enter the following cheat to unlock Invisibility: LEFT, SQUARE, RIGHT, CIRCLE, LEFT, SQUARE, RIGHT, CIRCLE. Press START to confirm code. If done correctly, the code will appear in the box to the right.

Unlock Slow Motion Mode:
Go to the Cheat Code screen in the Options menu and enter the following cheat to unlock Slow Motion Mode: RIGHT, SQUARE, UP, TRIANGLE, RIGHT, SQUARE, UP, TRIANGLE. Press START to confirm code. If done correctly, the code will appear in the box to the right.

Unlock Xen Gravity:
Go to the Cheat Code screen in the Options menu and enter the following cheat to unlock Xen Gravity: UP, TRIANGLE, DOWN, X, UP, TRIANGLE, DOWN, X. Press START to confirm code. If done correctly, the code will appear in the box to the right.