Very, very good. Gives you a dull spoon, half of the G volume of the Encyclopedia Britannica, and asks you to design a school for the blind. Marvelous.
A little on the easy side, overall...
Upgrading is too awkward.
I love the continuous wave button
Die once, die forever? No thanks.
Self-grading towers? Yeah!
... after 50 kills? Boo!
I have mixed feelings, but enjoyed it, none the less.