"We flew where their swords couldn't reach us" is so true. Incredible tower defense and very fun! At the start I didn't realize I had to upgrade the fortress and was overrun, but then I figured it out. Only small inconvenience is the fact that non-upgraded buildings look the same as upgraded ones, so I had to click on every one to check if it had upgrades. Also the earth tower is OP, unless it gets destroyed itself, NOTHING is going to break.