Not sure if any one else has said but, when you choose options from the "Start Game" menu (has three buttons top is "????" which is options, and the other two are both "??") there are three boxes on the left side of the options box which seem to dictate the graphical quality, the top one is low, and the bottom one is high (so of course the middle one is medium!
) Once you've chosen the quality settings click the bottom right most button to save the changes.