Anki

Anki is a fiercely independent, deeply entrenched open-source veteran titan that mathematically attacked the "Extreme Cognitive Optimization" market. It explicitly rejects the flashy, gamified UI of modern apps in favor of a terrifyingly raw, scientifically pure spaced repetition algorithm (SuperMemo-2). It is the absolute weapon of choice for hardcore medical students and polyglots who mathematically demand to memorize 15,000 highly complex anatomy terms over 4 years with mathematically flawless brain retention.