The top banner displays your current balance of coins and your coin production rate in coins per second (also displayed as cps). The display shortens the digit length by displaying 1,000,000 as 1.0 Mi, and 1,000,000,000 as 1.0 Bi, etc.
A coin bonus can also be collected each time the fusion bar in the top banner is filled, with the bonuses increasing each time. The bar gradually fills each time two cows are fused. Once full, birds fly across the screen and their poop counts as coins in the same way cow poop does.
Purchasing the tractor (with in game coins) from the shop allows coins to be collected for up to 2 hours while the app is closed. Further upgrades to the tractor can be purchased, extending it further to 4, 5 and 6 hours.
There are also in app purchases (i.e. they cost real-life money) which allow you to instantly double your coins, or double your coin production forever. Coin production also increases by 10% each time the universe is reset.