I would very much like to build a game that is known as 'Unblock' or 'Yellow Out'. It is a puzzle game in which the task is to move a car out of a parking space by moving other cars in certain directions.

These are links where the game can be played:

• Yellow Out
• Unblock

My questions concerning this game are:

1. Is this game actually licensed? I see it's available under two names (perhaps even more). Does this mean the game idea can be used freely?

2. Is there an article about it? I have not been able to find it on Wikipedia. I would like to gather some information about the game so as to understand more details of it.

3. Is there some database with puzzles available? I can just check the puzzles of existing games, but that's a pain because I have to finish a level to get on to the following one. I was wondering whether there is a general list of puzzles somewhere.

Thanks!