wow, congratulations, you published a game...maybe you should go read a book now

unsolo is right, the those 3 towers are noneffective, but its not an engine bug, the radius, measured form the center of the tower is to small, the creeps never get close enough, even when touching the tower. Just up the range by a small amount.

I also could not beat round 2 on hard...maybe just a little more start up money?

Aside from that, I think you've got a great start. I definitely want to see a lot more levels when you're done with this game.

Where is your map??

I think for your concept of space, the paths work...ships will be flying in all different directions rather than all ships following the same specific course.

I would suggest either lowering the cost of the towers and tower upgrades by a good 20% or increasing the stats on the stats on the tower upgrades. While the creeps do give you a lot of money, its just not enough maintain the towers for very long. As well, the very expensive upgrade costs do little in way of performance upgrade. I just don't think the balance is quite there.

I hope you keep working on this one; I think it's almost there.

Very nice. Great concept, but I'd give a more levels.

Nice. A little slow at first, and seemingly way too much money, but towards the last few levels I can see why. Good job.

Cod...yep, that says it all