Best TD game I've tried
This one made me want to come back for more, and more and more :)
Firstly, the game is graphically beautiful, with good, clear-cut colours that help make the game intuitive (green for Orcs, scorched brown for Hellfire and white with a bluish hue for Undead). Secondly, it's simplistic and straightforward, but with so many tactical opportunities, so that the game is easy to learn, but hard to master.
And finally, on the sound stage, it's excellent too, with good variety, and arguably some funny sounds in there too.
But with all things, there's still room for improvement and there's a reason I'm only giving you a 9, although I have to admit that it's difficult to figure out how to write the criticism on this point, so I'll just write what I felt might be short of "perfection":
1. I found the Undead Towers a bit on the overpowered side. Not only do the Undead Towers always seem to kill everything before the other towers have a chance, but they also quickly hog all the experience, which is slightly aggravating if you're me, who found the other towers' higher-level abilities more interesting visually.
This is a difficult point though, because arguably, this would just force you to think up creative ways of setting up defenses in a creative way which either does not include the Undead Towers, or places them in areas where they will serve mostly as a backup that doesn't really hog experience. So I'm still a little undecided on whether this is a problem or not.
2. An issue several other people have voiced is the Ninjas, or rather, the Ninja Champions. On one hand, they're an excellent means of forcing the player to keep a strong, central defense, and not just focus on destroying the attackers at the front line.
But on the other side of the coin, it's exasperating the player in a bad way, because no amount of careful planning can possibly ensure success, since it's evidently luck based whether or not the High-ranking Towers' special abilities (slow, freeze or scare) kick in at the very first strike; You can't hope to destroy the Ninja Champ at the Front Lines, because he's too tough even for the most powerful outer defense, and by the time his invisibility wears off, he's already on his way off with the stolen Gem.
3. I found many of the later waves to lack any significant challenge. The recurring problem seemed to be that later waves threw small numbers of high-level "regular enemies" at you. Unfortunately, these "Higher Level" guys were still too weak, because by that time, your defenses were insanely strong (only Ninjas could hope to get past the front lines).
I would recommend having actual mini-bosses which can be used in a group (lesser version of Champions that show up in threes or even fives) for later waves.
4. (*Joke*) I'd recommend placing the "advertisements" for your sponsors etc. during the loading screen (logo sequences play while the game is loading) - I've seen this done on other pieces of flash art, and although it arguably won't reduce the overall wait, it will at least spare us the aggravation of having a non-skippable logo-sequence placed AFTER the game has finished loading. ( :P )
Overall, I found the game very addicting and quite satisfying, not to mention inspiring to play. It could get a little repetitive at times (maybe if the towers result in different death animations - i.e. fire results in the victim running around in circles on fire and screaming until collapsing, Undead removing all but the skeleton, which then collapses into a pile o' bones, etc.), and a bit aggravating too, but the game provided plenty of reasons to go back and try again.
Improving on this gem would be difficult I admit.
Excellent work.