Update 1.7.5 is here!

-Extended dwarf campaign, meet the final dwarf boss!
-New upgrades including dragonlings evolution and powerfull charged attacks.
-Removed forced ads, added optional rewarded ads.
-GUI visual improvements.
-Added handicap system and difficulty levels to challenges.
-Mines are now permanently on battlefield with cooldowns, making it more user friendly. 

https://play.google.com/store/apps/details?id=com.EliamAndTaidaGames.MadDragonDefense&hl=en