Building a spaced repetition / incremental reading / video / podcast / audiobook app. I wanted a better UX version of SuperMemo basically. Something I actually enjoy using myself to explore topics incrementally. It uses the latest FSRS algorithm (FSRS-7), and also supports SM-20, SM-18, SM-2.
https://en.wikipedia.org/wiki/SuperMemo
https://github.com/melpomenex/plethora