Picks are a currency gained from tapping or swinging your Pickaxe. Swinging will award more Picks.
Each swing gives an amount of picks equal to double the picks received from tapping. The picks gained from swings are shown in yellow on the screen.
Critical hits are occasional stronger hits. The chance of one occurring depends on what pickaxe is being used, but the chances can be increased through the Critical Strike Potion. Critical hits grant 50% more picks and double the Pickaxe's damage. The picks gained from critical hits are shown in orange on the screen, regardless if it came from a tap or a swing.