Couldve Been great; Just A Cash Grab.

This game is best suited to players willing to pay to progress or those with the patience to be in it for the long haul. Its beautifully designed and well thought out, very stable with no crashes. The game has been acquired by a new company and I hope they implement a more balanced approach but Im not going to hold my breath.
Very enjoyable initially but then gets unbalanced in the Bird levels and seriously so in the Serpent ones to coerce IAPs. In fact, its impossible to progress in the Serpent King Tower without paying up serious cash.
Worst of all, 75% of card drops after much grinding are worthless. Even if you buy them, chances are youll get worthless ones. I have dozens of cards Ill never bother upgrading. Then, it will take at least 3-4 days to upgrade to the higher levels of the more useful cards (which will literally take months to acquire in the first place). And, you can only upgrade 1 card at a time!! Theres a huge amount of content but, a lot of it is quantity over quality. The arenas and outpost maps are boringly repetitive and you will have to play them hundreds of times (Ive played the various arenas over 2000 times!) to be able to obtain any decent cards.
You can buy gems to speed up card upgrades but will need to spend at least $50 on them if you want to quickly upgrade a couple of cards to the higher levels. I bought some gems but, the cost of upgrading cards is so high that I went through 3000 gems in a few minutes. Be patient and enjoy the game for what it is but dont bother buying gems or cards unless you have hundreds of $$ to waste.
Yes, Devs deserve to make money but, their shortsighted greed has ruined what could have been a truly excellent game. I would have gladly paid upfront for a couple of levels and more periodically for extra levels. Balanced gameplay with the option to pay to progress more quickly would have been a better strategy rather than trying to coerce us into it.

Starman6 about Crazy Kings Tower Defense Game, v1.14