When I was looking at the page for controls and saw "Zoom In/Out" there I was confused, as this just changes the scale of the web page. But when found out that it was incorporated into the game was I like, "dev, you are a genius!".
Sometimes zooming would cause my browser to take control away from me, but did not happen enough to be a real problem.
I do think that the text could be made a bit bigger (the shop menu was a bit hard to comprehend). But other than this, I really enjoyed your game.