It was OK
The gameplay is old, but I must say I like the idea of ancient stones on an island. The abilities were good too, but quite unbalanced. The first two stones really suck, since they don't do THAT much damage within a reasonable radius. Savind 400 for the laser is much more profitable, especially with some ice towers next to it.
Besides that, a higher number at speed means its slower, but with a high number you expect high attack speeds. This is quite confusing.
Next to that, I experienced a hell lot of lag (100% cpu use) with only 4 ice towers and 5 lasers, with low quality settings! Since I have a quite good PC (2.0GHz Dual Core and 9600GT) it shouldn't be a real problem. Try taking a closer look at your scripting, it could probably be improved a bit.
Finally, I really dispite there are only 50 waves. My base got solid real quickly and ready to be upgraded, and then it just stopped!
Also, maby you could try to make the loop really looping. Now it just stops then replays. I don't know a lot about audio so can't help you there.
Besides those points, I really enjoyed playing this game. 2/5 and 6/10 because of the points I mentioned. If you'd improve it I'd give it a 4/5 and 9/10, because the whole idea of the game isn't new at all. Judging a game is based on e.g. graphics, playability, and yes, originality.
Hope my review was helpfull, besides, that's why we're here on NG. ;)