This seems like the beginning of a good game. Like some of the other commenters, I think it would be a good idea to separate your resurrected enemies from the living enemies. Also, all of the units, both mine and the enemy, got clumped together on the tower, making it even harder to tell which of them were alive attacking me.
Using this as a springboard, here are some ideas for the future:
- Make the base enemies move slower and make the base undead target enemies rather than run in circles.
- Add a spell that places a marker on the map where a couple of your undead will collect and make a wall out of themselves.
- Have the enemies appear grouped together in distinct waves instead of constantly appearing at random intervals. (at least, that's how it seemed to be working. I never saw another anything say "Wave 2" was starting