Fun but frustrating

A simple gem swap concept to battle against monsters, but has a bs mechanism where you battle for 10min, whittle a boss done to a quarter life only to have them deal 100x more damage than ever before to kill anyone outright, thus forcing the player to buy gems to keep playing else lose progress. Id even buy gems if I knew they wouldnt be wasted by such a cheap gimmick

Richard Coxford about Puzzle & Dragons (English), v8.5.2