[lloydatkinson]

A long time ago when Lego used to produce actual video games (or at least, had game companies do it) one of the games was Lego Loco - a game that I probably spent possibly thousands of hours playing as a child along with all their other games.

It had the concept of being able to send postcards and trains that you made in game to either people on your LAN or to a random player on the internet. Their trains could then move around on your railways - and you could send it to back to them or anyone. The trains would go in and out of train tunnels.

Your comment reminded me of it.