Horrible. As someone in Builder's Workshop that doesnt want to spend real money on the game, getting gems is difficult. Luckily, I had 50 of them which was just enough to retry the Mighty Miner challenge. However, after losing once I tried to change my deck but the second attempt autostarted and I lost due to having the same bad deck. Then, the game just crashed halfway through the third game raking 30 seconds to reopen to the loss screen. A waste of 50 gems from 2 stupid issues.