What are some popular gaming apps in China?

Hello! I am from Australia and I gifted some tablets to my cousins back in China. However, I forgot that Google cannot be used and my cousins had no way of accessing their tablets, sending them back to me so I can help fix/set it up for them :(. I have just decided to help them install apps for now but I am not sure what games or apps are popular in China. Do you guys have any suggestions?