There are a few games out there that let you earn real bitcoin. The most popular one is probably Bitcoin Billionaire, but there are others like Blockchain Game and Cryptokitties.
Bitcoin Billionaire is an idle clicking game where you earn bitcoins by clicking on the screen. The more you click, the more bitcoins you earn.
There is also a chance to earn bonus bitcoins by watching ads or completing offers.
Blockchain Game is a strategy game where you earn bitcoins by building blocks of transactions and verifying them. The more blocks you build, the more bitcoins you earn.
Cryptokitties is a collectible game where you can buy, sell, or breed virtual cats. Each cat has its own unique set of genes, which determines its appearance and characteristics.
You can earn bitcoins by selling your cats for more than you paid for them.