's spin on the classic tower defense game is, well, the spin. Instead of the flat 2D map you are used to seeing, you can now play on a 3D planetoid. There are 34 planets, each one more difficult than the last. Your planet is being invaded by the Suona, an alien race apparently bent on your destruction, one colony at a time.
You will gain access to 10 different defense towers. Each one has a unique defensive purpose, and are all upgradable. Your mission is to place these towers in such a way that the oncoming invasion is stopped before reaching your colonies. It is very convenient to know exactly where your enemy is going to land, but hey it is a game.
There is more than one colony on each planet. As you unlock new planets, you will also increase the number of colonies you will have to defend. Don't think the Suona are just going to take all of this lying down. As the types of towers you have access to increase, and you unlock new planets, the Suona will come at you with newer, tougher ships. This is fine, because you will also gain access to super weapons that are capable of killing many ships when detonated. These should be reserved for special situations during the battle.
If you are familiar with other defense games, one thing you will need to adapt to here is the speed. The action is not turn-based. It is all live action and on the go. You get a short initial set up timer, letting you know when the waves of ships are coming, but it is up to you to keep everything moving as they press their attack.