The app uses inconsistent romanization and crappy computerized pronunciation audio, making it impossible to actually learn how the Hangul syllables should be romanized or pronounced. It doesn’t explain any of the rules around voiced and unvoiced consonants, aspiration, consonant doubling, or pronunciation changes in final consonants - the hard parts of learning Hangul. Sections 2 and 3, on final consonants and vowel combinations, have their labels swapped. The writing exercises sometimes reject correct input for no discernible reason. The timing of the spaced repetition system is not explained anywhere, so you just have to guess when new reviews are coming up. If a character is incorrectly recognized as correct, there is no way to mark it wrong. The exercises include pretending to input Hangul on a keyboard, but the app highlights the correct keyboard buttons, so you don’t have to actually internalize how a Hangul keyboard is laid out. Most of the multiple choice questions do not require you to decipher the entire Hangul syllable - they can be answered if you know only the initial consonant of the syllable. In conclusion: useless!