I think that by the time B has gone once around, A will have gone 1/6th around, then B just has to go that 1/6th further to catch A, but by then A will have moved further ... oh no, will he ever catch A?

That's what I was thinking!

I got that, but edited it after about 2 minutes.

Or even longer ... give all visitors a chance.

(Wow, B DOES get past A ! )

The text could be the same colour as background ... I could delve into PunBB code to see if that is possible.

It may or may not be hard, depending on whether I can apply the "current" background style to the text. I won't know till I have a look.

And I don't know how to extend BBCode, but there should be a way.

Hmmm ... what would we call the BBCode?  [ ??? ]

You can do it in PHPBB, so I expect it's possible on PunBB. Perhaps editing the CSS, if you can?

They will cross each other at 7:42AM.

I like those names.

Apparently the search engines HATE invisible text because spam sites use it to misdirect people to their site. You know, mention important words several times at the bottom of the page even if it isn't part of the site. So advise I have seen said you can be banned by the search engines for using it.

So, I have thought "what about just hard-to-read text?" You know it is there, so no deceit, but you have to run your mouse across it to read it or something.

So maybe White Text or some clever "CSS" stuff.