FlashZen is a browser-based flashcard tool built for vocabulary acquisition in English and French. It ships with 800+ curated high-frequency words organized for progressive learning, so you're not wading through random word lists. The interface is minimal — just the card, the answer, and a rating. Under the hood, a spaced repetition algorithm schedules reviews based on how well you know each item, so time spent studying is focused on what you're actually forgetting. Beyond the preset deck, you can add your own words with custom definitions or translations, making it useful for domain-specific vocabulary (legal, medical, professional). The standout feature is sentence generation: once you've built up a known-word pool, FlashZen generates practice sentences from those words and flags errors in your responses — a practical step toward active recall rather than passive recognition.