Hidden away somewhere in my attic is an old Xbox 360 that I'll never throw away. On its hard drive is a Minecraft save file that contains the first house my oldest son ever built in the game. He was seven and, coming from a boy on the autism spectrum with a limited vocabulary and no patience to draw and paint, his creation was a revelation. Sure, it is a monstrous carbuncle, a mess of wooden planks, cobblestone and dirt. But it is also the greatest building I ever saw.