Thanks for the quick reply! It's a great game for what it is right now. I'm sure you'd hear a lot more back if it was free - but that comes with it's own consequences.
One more thought based on what I read (assuming from you) on Reddit. You don't have to introduce 3 new buildings at the end of level 1 if you want to space the content out more. I think the idea of adding a new mechanic to every level is great (with maybe 20 levels overall).
One thing I'd LOVE to see though in the next update is an "infinite" mode where you see how many waves you can last for.
Thanks, and looking forward to the next update!