Turn on the store-bought tablet PC that Jepsen's prototype screen sits in—she removed the old screen with a screwdriver and swapped hers in—and it looks and acts like any LCD screen, because it is an LCD, only better. LCDs display color and video, but they kill battery life. Electronic ink is more energy-efficient and paper-like, but it's black and white and is frustratingly slow to load a new page. Jepsen's screen combines the best of both technologies. Flick a switch, and the bulb that makes the screen glow will dim. But instead of going dark, only the colors will fade. That's because in Jepsen's screen, ambient light can substitute for backlight, bouncing off the mirror-like material that Jepsen has added to each pixel to reflect shades of black and white. With the lamp completely off, the screen, called 3Qi (pronounced "three chee," as in qi, the Chinese word for "spirit," and a geeky pun on the 3G wireless network), displays letters as crisp and readable as those on Amazon's Kindle. In this mode, 3Qi uses about one fifth the power of a normal computer screen, Jepsen says. And unlike the E Ink–based Kindle or any other widely available e-reader, it still does everything a regular LCD does, including play videos.