Pretty challenging game. You have a lot of way to design your strategy.
There are several different UI. One of them is agressive the other one is tricky. The Skyabove Bosses, the Dragons and the High Bosses are really tough. Not to mention the Pandora where you have to create a deck on the fly and fight your way through 6 battle if you can. The Puzzles on the other hand teaches you a lot of tricks that you will need if you want to be success in the game.
The interesting part comes when you co-op with other players or when you play against them.
As far as I see, there are only 30-35 active players in the game, but the discord channel is pretty active and useful.
The DLCs are worth to buy from the very beginning. You can develop much faster with them. You can get more points with them which means +20 free levels.

It's a creative game with cool mechanics, pretty artwork, and it's fairly easy to get all the cards. There aren't as many people playing as in the past, but I've consistently been able to find matches.

Addictive game.