Thank you for playing. I'm glad you like it :) And thank you for your thoughts!
It is possible that you lost, because you lost your dragon. When you lose your dragon you will lose 10 Gold Coins, because the dragon has so much damage and health.(By the way it is a 10 percent chance to get a dragon by mutating cards.) When you lose other units, you will lose 1 Gold Coin. So you have to plan, how much Gold you will spend and have some Gold Coins stored to prevent losing the game.