My 12 year old has expressed an interest in writing his own programs. So I'm doing a bit of research to find what people reckon is a good platform for him to dip his toes in the programming pool.

I'm looking for something that is pretty quick to pick up the basics of, and will have some fairly immediate payoff to hook him in - so that he can see results rapidly, then go on from there.

He has the attention span for it, given the hours (and hours) he spends playing Minecraft, downloading mods and new worlds for Minecraft, researching new tricks to use in Minecraft and watching walkthoughs on youtube of other people's Minecraftery. He likes Minecraft.

His teacher has given making a computer game on a topic relating to a book the class is reading as an option for a project. That's about all the information the teacher gave, something like "write a computer game, I have no idea how, but I'm told it can be done, go for it".

This is a chance for me to steer his computer addiction into a useful direction.

Any ideas from the pros? I'm in IT, but not a programmer, so I don't know if one of the major platforms would be a good starting place, or if there's something more basic (like BASIC when I was a lad) that would be a better place to start. I remember programming in LOGO when I was in school, geez I'm old.