Really? I'm using Firefox and it's working. I just refreshed the page and it went further and further until it finished.
I'd love to have this be co-op. I've been looking for a simple farming/survival game like this I could play with a friend of mine.
You need to make more furnaces and forges for more things. Shift allows you to craft half of max and left ctrl makes the max. Or do you mean you can't make more than one item of a single item?