As others have said the sound design is so good! I'm not usually one for clicker games but i enjoyed this one and played it all the way to the end. I can see this being built out into a full blown game with more upgrade options and goals.
I did come across a bug where the menus (options, instructions, selecting upgrades, etc) would overlap if i tried to open a new dialog without closing the previous. Other than that, the game ran really well and felt polished!