Lexi is an iOS game that trains vocabulary via crossword puzzles generated dynamically via spaced repetition. In the game, the user's learned words accumulate as stars in the zoomable pannable sky, with the app having an astral theme. Crossword clues take the form of a fill-in-the-blank sentence + evocative hint, training in-context application of words rather than rote memorization of definitions. Each word has its own word-card with an evocative image, a definition, and an example sentence. Words are clustered into so-called "confusion classes", being groups of mutually confusable words whose nuanced differences are trained through contrastive learning drills, and which correspond to constellations in the sky map. The game is primarily designed with single-player in mind but it also has multiplayer. It has profile pictures unlockable through learning adjectives that name them (e.g. unlock "Astral Fox" upon learning "Astral"). It has friendlists and DMs, forums, leaderboards, and saved collections.