> Or simply nothing, and the surprise of the user when he press "Right", "Left" appears :)

Yes, I think I'll try this. Hopefully it is a good surprise when it happens. :)

But I hope it shouldn't cause any problems, because there isn't really any reason to normally be clicking those areas a second time once it is already highlighted.

The main problem is that it isn't immediately obvious that it is possible to do it. But that's ok in some areas that are not completely essential to basic operation.

- Michael