Incredibly addictive and simple game that, though very short and somewhat easy, leaves you playing over and over again.
The controls in this game are the most simple and easy to use controls I have used in a long time. There are three basic commands that are really all you need, though there are more complex commands. Hold the left mouse button and drag from your asteroid to another to send ALL your units. Left click an asteroid to select it and see detailed information. Right click an asteroid a certain number of times to count the number of seeds you want to send, then left click the asteroid you want to attack. And aim the mouse and scroll in and out with the mouse wheel to control movement. Brilliant setup that flows smoothly and naturally in the game.
The game itself appears very simple but there is great deal of strategy required in the beginning of each level (by the end you should have a large mass of seeds that you just steamroll enemies with) In the begging you have one planet. You have to explore other planets to find the weakest enemies to conquer. You also have to choose what planets to upgrade with more trees and what type of trees (defense of reproducing) Then you need to know where to hold your units in case of an attack so you can respond quickly. Now the AI is usually very dumb, but it has its moments where you will find yourself moving seeds around as fast as you can trying to save an asteroid from capture.
I'm rambling on though. Case in point you really have to try this game to understand how fun it is. It is incredibly short (took me around two hours to complete the five levels the first time, but I have replayed it several times) Plus its FREE. Can't go wrong with that.