Thank you, I'm a bit torn if I make a new game -- as to whether I'll reuse the same gameplay, or invent something new! But, I'm leaning towards something new.
Personally my favorite puzzle games tend to be action puzzle games, like Puyo Puyo, Magical Drop or Tetris. I'm currently working on a game like this but think people appreciate Monster Mind because of its chill vibe, so a different kind of chill puzzle would be more suited for its sequel. Mahjongg is an OK choice, it could be fun with a social aspect! Although I think there are already many games like that. I'd like to make something unique!
Personally I really like puzzle and rpg porn games since I like to play one handed. *Wink wink nudge nudge poke poke* And match 3s tend to be my go to, Huniepop did a great job with it, too bad the writing in the sequel went... weird. There was a tetris attack game called Octofurry that was pretty good.
I'm not used to thinking of Mahjongg as social (just played mahjongg solitaire) but that could be really cool, you with a few characters playing together, especially if they had fun with each other, but probably a lot of work. Especially if you did animations with similar quality to Monster Mind and both gender options.
There is a game called Otoko Cross: Pretty Boys Mahjong Solitaire. It works decently, you win, clothes come off, but its really held up by Mahjongg solitare just being fun if frustrating at times. Would be more fun with your characters, making comments and getting more and more excited as you get closer to winning or building up a score or something. Maybe if you get close but lose they end up cumming themselves instead of being able to hold it for you to have fun with them.