A relatively primitive version of what we call heads up displays (HUDs) has existed for decades. First in use by the military during World War II, a reflector sight projected the image of a target in the eye-line of a fighter pilot, ensuring a clear and undisturbed focal point at the most crucial moment of attack, allowing a pilot to act with precision, a heightened degree of safety and, more importantly, a higher certainty of success. This early use captured the essence of what future HUDs might do: impart crucial information in the moment it was needed, and in a way that wouldn’t distract the user, enhancing and not detracting from, the experience.