My thoughts as a player :)
at first (i skipped the tutorial)
i wondered what was going on, the interface was pretty confusing
however i then sat and played until about day 29 and got thoroughly sucked into game play (until my boss came into my office and i thought i better close it down)
great little game, really challenging, and i enjoyed it
some different cannons would be awesome like a spawn cannon which you could spawn minions from for the sequel!
or a paying for defences so you could ignore a couple of rolling balls
great work! I am going back to it to get the most out of it now i know what is going on!