[mavlee]

You can move by dragging either end of the mirror. It's not entirely obvious, maybe an easier way to move the mirror would be helpful.

[anigbrowl]

Yes, this is painful as is. Also, when I complete a level the entire frame shifts about 10 pixels to the left as the save button appears. Nice concept though.

[byronknoll]

The left shift is probably due to the scroll bar appearing (since the save button makes the page slightly longer).