Survive 30 consecutive waves with at least one co-op player.

Complete act 4.

Explore the entire island.

Heal yourself with a medkit 100 times.

Complete act 2.

Kill 250 zombies using edged melee weapons.

Kill 50 zombies using a vehicle.

Find 60 collectibles.

Use the vent system 20 times

Use the revolver

Escape from android combat without taking damage

Encounter the Alien in Sevastopol for the first time

Construct an item