Every word climbs through levels of increasing difficulty: 12 levels for a normal word, 25 for a word with a character such as a kanji, and a short track for flip cards. Early levels use multiple-choice cards, first recognising the foreign word, then choosing the native word in reverse. Mid levels add puzzles such as typing a missing letter, finding two swapped letters and sorting scrambled letters. Higher levels ask you to type half of the word and finally the whole word from memory. A correct answer moves a word up one level, a mistake moves it back a few levels, so harder words simply get more practice until they stick.
Looking for step-by-step instructions? Read the vocafox manual.