Expensive game. Can't progress without gems, additional energy, additional items such as talismans, extra energy, etc. Some items are offered in gifts but if you try to get any progress, it can't be done in one session. Also, games increase in energy needed. I tried one goal and the energy needed was over 100. Difficult when the level was 210 in reserve. Higher amounts can be earned but you can't play without energy. One book isn't finished before the next ones need to start.