Money Grubenthe app just strong arms you into needing to buy Hearts constantly. You get 5 hearts per day so you cant make more than 5 mistakes or you have to handicap your learning practicing words miles below your skill level to get only 1 heart so never make a mistake . Constantly takes advantage of audio only exercises to give you words they haven't taught you to drain your hearts. Completing streaks gives 50 gems...it takes 350 to refill 5 hearts and they jack up the price by 50 each time..