Everything is good, except the saving method. Please change it. Oh... maybe you can make it available for Android too? Using Cordova or something else.
Sorry, I’m aware of the save file losses in the browser version. If you’re not going to use the downloadable version, I recommend downloading your save file from Menu → Export → Download after each gaming session. This will give you a .txt file, and if your save gets deleted, you can import it again. At the moment, I can’t provide any other solutions for the browser version.