Thank you for reporting that! I will look into it today. I was inspired by Subway Surfer with the endless runner concept, and Spelunky with some of the graphics.
Edit: I put out a patch to make gas clouds less laggy and *hopefully* fix the store from freezing up. The frozen store bug was hard for me to reproduce, but it did happen about one out of ten times when I played. I moved some things behind the scenes that should stop that from happening again. If it still happens, you can just refresh the page and it will remember how many coins you have. Again, I appreciate your testing and thoughtful feedback!
Edit 2: I fixed the store 100% for real this time!