It's fun and has a good presentation. The swordsman has a nice attack animation, but it does not reveal the attack range. It's actually a good point though, I think this adds some challenge to the game and force the player to guess and get a feel to when it's time to attack.
The dificult seems a bit random though. My best was about 290 seconds on my sixth round but it's because the zombies that spawned were in general slower than on the other rounds.
Anyway, good job on this!