Ask HN: Help – Does anyone remember an app was shared here about words for iOS?

I vaguely remember an app being shared here a few months ago that the author made to remember words? It was like a thesaurus or dictionary, but had very pretty animations. It was also paid but maybe it was open source too? I remember thinking I wanted to see how the app was made later and never got around to it. It was made with Flutter or React Native, and the developer might have been European. None of this information is reliable btw, I may be mixing up posts.

In a related discussion, do you bookmark interesting hacker news articles? This is the first time my google search / reddit search / algolia hackernews search has failed me so completely that I need to make a post asking for help.