Halves is about variety. The first two chapters are always the same, but at the end of the second chapter we have to choice. That choice is a different level you can play, and at the end of this chapter another choice... This means multiple different games and endings. Every level try to be completly different in mechanics, you can be driving around with a van being careful with your hunger and fuel or being killing zombies and searching for ammo and health kits, for example.
How choices affect the game