A lot of, and pretty addictive. I stayed up all night playing it, and didn't even realize it. x-x'
Naturally when you first start you're gonna want to play as the Huntress or Monk
Dont.
If you want to get a feel for the game, and get the damage dishing out, used the Apprentice, or my fav, the Squire.
There is a reason why the other two are labeled "Advanced"
They are much harder to play with, and they don't have cool towers, just traps. More like support players.