Pretty good intro into mahjong.
My only gripes with it are just nitpicks, like the overly moe art style and the fact you can't play in portrait mode, but otherwise it's easy to jump into and fun to play.
No comment on the gacha stuff, I'm not touching that unless they rerun the Akagi collab.
Update on the gacha: Tried for the Code Geass collab. I hate this gacha system.