Very nicely done
When you play a tower defence you always try to find something that makes the one your playing unique. The one that made this stand out from the rest was the fact is your seigeing instead of defending. The music was nice, art was good and the contantly extending castle upgrades was awesome. I loved the rainbow upgrade XD
Other then that well done '<(^_^) thumbs up to you. Only one thing if you ever make a sequel can you add more then six units? Don't get me wrong they are good and all but 6 just doesn't feel like enough. :3