Click the green flag to start the game. You start out with 0 diamonds and 0 Diamonds Per Second. Click the diamond to get diamonds. Go to the store to buy DPS (Diamonds Per Second). Every time you buy DPS, the price will increase. The starting price is 10 diamonds. The next price will be the price it was before multiplied by 1.5 then rounded, or round(1.5 * DPS Price). DPS will increase your diamonds by 1 every 1 / DPS seconds. This works because this is the same thing as 1 * DPS, which is just DPS so you get the same thing either way.
Same project, but hacked. Rebirth changes your diamonds by 3 * the amount you have then raises 10 to that number.