This site is designed to take advantage of CSS. If you are seeing this, CSS must not be available or enabled in your browser. Everything should still work, but won't be as pretty. :)
With Undo: Rewind a working step will be revoked. In
principle the whole mechanism behaves in a similar way to a recording
on tape or compact cassette, where any recordings made can be rewound
at any time to play them back or make a new recording.
