An upgrade is an item that can be crafted together with machines to increase their output.
Upgrades go in tiers:
Upgrades must be done sequentially. (i.e. you can go from iron to gold, but not from stone to diamond)
Ad blocker interference detected!
Wikia is a free-to-use site that makes money from advertising. We have a modified experience for viewers using ad blockers
Wikia is not accessible if you’ve made further modifications. Remove the custom ad blocker rule(s) and the page will load as expected.