Turret button

Turrets slot are places on your tower for extra turrets if you click this button ---------------------------------------------->

on the top right of the screen then it will add an extra turret slot. At the begining you atomatically start with one turret slot. You can buy another one for 1000 Gold. The price does go up so the next turret slot that you buy costs 3000 gold. The next is 7500 gold.