The save feature is experimental! Due to how browser works and the limits in memory, please note that it could crash your browser.
I'll try my best to fix all of this, but there is no garantee that it can be done.
For Chrome users, if you open the console by hitting F12, you will be able to download the save game without crash (Yeah I know...)
For Firefox users, you might get a button telling you to Wait, just click wait a couple of times, and you will get the save game.