I like the defenders having health and not always going down in one hit. The addition of the building aspect of this game is quite surprising.
You've created a means for someone to create a kill box and funnel the enemies in.
Is that what the walls are for? You have them cost 3 coins, and they block arrows. Someone can't sit behind them and shoot. If you could shoot over the walls, I'd use these. They're in a very early state, though. Perhaps new variants will exist in the future.
I applaud how you did something new.
They're cool to have, but 3 elemental defenders gives you more bang for your buck. The elves are meat shields, just the same as the walls are.
The defenders being able to use elemental effects makes them so much better.
My favorite thing is the increased detection range. These guys used to be useless because they took too long to aim and fire, and by the time an enemy walked up, they'd already be dead.
They're still best used in large groups, but the fact that they can see a foe from farther away now means you get more use out of them.
What are the differences between the types of towers, by the way? Is it listed anywhere?
Also, is it a bug that enemies can spawn outside of the map? If you go to the corners, imps will spawn and try to force their way through the barrier there rather than appear in an open space.