Nearly 10 years ago, on a hot June afternoon, I was standing on a Los Angeles street corner waiting to be let into a top-secret Microsoft briefing. On the floor, someone had chalked a line of rectangles, leading to the door. What did they mean? . Those rectangles were the first sign of what was to become Microsoft’s line of Surface devices, at first with the familiar 16:9 aspect ratio, but soon transitioning to a more tablet- and document-friendly 3:That display has been the heart of Surface and is key to understanding how Microsoft thinks of its devices: a surface where we interact with applications and content. .