Chapter achievements. Every chapter has a specific achievement / requirement.
Requirements of Each Chapter
- Chapter 1 - Kick enemies (5 of them) off the cliffs (kind of broken, you have to delete your save and do it on first try I think).
- Chapter 2 - Don't use guns at all.
- Chapter 3 - Open all doors with kicks.
- Chapter 4 - Take the torches off the wall, kill everybody.
- Chapter 5 - Kill enemies in the fire.
- Chapter 6 - Don't kill humans, kill only monsters.
- Chapter 7 - Beginning of the level, let the 2 monsters kill the humans.
- Chapter 8 - Kill every enemy on greenhouse area.
- Chapter 9 - Be quicker than the big guys in Chapter 9 (?)
- Chapter 10 - Don't break any glass tube in the laboratory.
- Chapter 11 - Drop enemies into fans.
- Chapter 12 - Kill enemies with all the barrels of acid.
- Chapter 13 - Kill some enemies with the grinder (enviromental).
- Chapter 14 - Let the boss destroy the walls and the achieve should pop.
- Chapter 15 - Kill enemies with all airplane propellers.