Being a collect-a-thon, Yooka-Laylee will not be the same length for every player. Your mileage will vary depending on how thoroughly you'll play through each level.
However, if we're talking the barebones, you'll need to collect 100 Pagies total (which includes Pagies you already used to unlock and expand worlds) in order to gain access to the final…
Atlas is an action-rpg with rogue-like elements where you use your ability to control the ground to fight the enemies and move through procedurally generated worlds.
