Slow learning curve in the beginning but once you get the hang of it, it's gripping. Great pacing in the tutorial. It started simple and kept piling on the layers neatly.
Minor criticism: the resolution should've been higher so that the graphics could've been magnified a little more as the screen feels a little crowded yet still small.
I can't believe how well thought out this is from a logical and competitive perspective. I'll be playing this on and offline with silly pieces of paper instead. I'd buy it if you made it into an Uno-like card set.