Very good, with the need of some improvements.
It is a nice TD game, but there are some small things that should be improved.
1. A sience facility where you can upgrade your income, lower the costs of your troops/turrents and unlock the things on point 2.
2. Some passive weapons like mines, energy nets (stop enemies for a while, or some rays that slow them down.
(Optional and only a wish ;) ) 3. I miss some twists in the campaign, where aliens or original inhabitans try to stop the colonists on both sides, but maybe there will be one at all, i haven't had the time to complete the game, but will catch up to do this.
Other than that its very nice to play. :)