The "is this prime?" game (https://isthisprime.com/game/) recently passed 3 million attempts, which I might not have noticed if Siobhan Roberts hadn't written this lovely article about it: https://www.technologyreview.com/2021/07/18/1029440/prime-number-game/
I like how they embedded the game in the post!
The social network of the future: No ads, no corporate surveillance, ethical design, and decentralization! Own your data with Mastodon!