What is Reddit's opinion of Hanafuda KOI KOI Free?

From 3.5 billion Reddit comments

There's a game called Hanafuda Koi Koi (the actual name is just Koi Koi) that's fun to learn and play. There's no tutorial though, so I'd recommend checking out Wikipedia.

This is the app I use the most to practice: https://play.google.com/store/apps/details?id=com.thresholdjp.hanafudafree