ACHIEVEMENT - HOW TO UNLOCK Serious Beginner (10 points) - Beat any level in single player. Game Master (20 points) - Beat the game. Serious Sam (30 points) - Beat the game in single player on serious difficulty. I am Invincible (10 points) - Beat the game in single player without firing a single bullet or shell. Serious Run (15 points) - Beat the game in single player by beating estimated time on each level. Metropolis King (20 points) - Beat Metropolis level in single player on serious difficulty without loading. Cannon Expert (5 points) - Pierce at least 10 enemies with a single cannonball. Perfect Kill (10 points) - Kill all enemies in Karnak in single player. Look, It's a Secret (30 points) - Find at least 50 secrets in single player. Co-op Beginner (5 points) - Beat any level in co-op. Co-op Hippie (10 points) - Beat The Great Pyramid in co-op with blood option set to hippie. Serious Co-op (35 points) - Beat a co-op game on serious difficulty and extra enemy strength on 400%.