This isn't the standard tower defense you're looking for. Champions and other goodies give this more character than what you find in other mobile games of its ilk.
At the recent Game Developer Conference Europe in Cologne, I met a lot of developers with creative and innovative ideas. Some of these ideas could have a big impact on the game industry. Unfortunately, most of these developers were making easily avoidable infrastructure mistakes, like building onsite rather than in the cloud — a shortsighted decision that greatly hinders their ability to scale.