Core gameplay needs work.
I feel that 'Defend your Castle' was a superior game, thanks to it's nice stick-man flicking. You try to incorporate that here, but your characters lack inertia when being flung around and so the gameplay itself isn't quite as satisfying.
There's little encouragement to use the magic spells and the cost of runes is a real put-off. It may have been an idea to simply have some sort of MP that were constantly replenished.
Although most things can be worked out easily enough, it would have been nice to see more help - explanations of stuff. Also, after clicking on 'next page' it would have been nice to be able to go to the 'previous page' rather than just the 'main menu'.
The gameplay just doesn't change much and it isn't enjoyable enough for that to be the case.
Also, the graphics could be better.
On a more positive note, I felt the game was fairly solid in terms of coding and seemed an achievement in itself.
The fact that upgrades start to cost more is a sensible move, and I remember it being an omission in DYC.
The spells could set it apart a bit (although if you want them to be a more significant part of the game, having MP which replenish might be a good idea, as I noted above).
Overall - very impressive game. I can't imagine the amount of work that must have gone into this.
But, from my viewpoint, your work hasn't paid off... yet. With a few tweaks, I'm sure it could surpass the inspiration.