Zombs.io is a kind of tower defense game with elements of survival. So, your main goal is to stay alive as long as you can. You need to build a base, upgrade it and protect against zombies. Zombies will start to attack you when you built the gold stash.
Before that, you can gather resources and find the perfect place to build the base. This place should have a lot of trees and stones for mining. After the gold stash is built, protect base as hard as you can. Build walls, defensive towers and gold mines that generate gold, use it to upgrade your towers.
Zombies will attack your base only at night and each next wave are stronger than previous, so you should be ready. Keep in mind that you can join the party with other players, so the game could be even funnier. Enjoy the game!