Super fun!

I installed the game after a friend who plays it for points recommended it. I basically play without spending money, so I progress slowly, but it's still fun. Just logging in daily and using the maximum amount of fast travel really racks up the experience points. For stages that require cooperation, you can get a lot of rewards just by recruiting someone to carry you, which allows for rapid strengthening and makes solo stages easier to clear. Players who spend money are stronger because they spend money, but I think it's a game you can fully enjoy even without spending anything.