Update with local data saving

This is a quick update which switches the online data saving in the original version to a local data saving system. This is mainly because changes to Google Sheets and javascript have resulted in the original system no longer working. However, as the intention for this game was that it would be hosted on a single device / screen in a physical museum space a local data saving system will work for the game.

Other minor updates include improved constrast and slight changes to images and sound used throughout.