Each kanji, verb and word has a success rate (correct ÷ total answers) that updates after every test. After 3+ answers: Easy = ≥85 %, Hard = 60–84 %, Pass = below 60 %. Items that are Easy/Hard/Pass appear 2–3× more often in the question pool — so weaker items show up more frequently until you master them. New items (never answered) also get a small boost to appear early. Skipping a question twice grades it as wrong and marks it Pass. Progress is only saved when you finish a test — leaving mid-test discards all changes for that session.