How do you merge units?
theres two buttons labeled "merge", one is for merging tier 1 units, and one is for merging tier 2 units
once you click the button, you need to select 3 units, either by clicking at them directly, or in the unit list.
when the button says 3/3, you can click the button next to it to buy the upgraded unit (if you cant afford it, you cant finish merging)
