text: Caitlin headed into her bedroom first. She knew that parents of teenagers often complained about how messy their rooms were, but hers was immaculate. It had to be; the only way she could ever find anything was if it was exactly where she'd left it. Bashira had been over recently and had asked to borrow a tampon—and then hadn't left the box in its usual place. The next time Caitlin needed one herself, her mother had been out shopping, and she'd had to go through the mortifying experience of asking her father to help her find them.
  
  She walked across the room. Her computer was still on: she could hear the hum of its fan. She perched herself on the edge of the bed and motioned for her father to take the seat in front of the desk. She'd left her browser open to the message from Kuroda, but couldn't remember if the display was on; she didn't like the monitor because its power button clicked to the same position whether you were turning it on or off. "Is the screen on?" she asked.
  
  "Yes," her father said.
  
  "Have a look at the message."
  
  "Where's the mouse?" he asked.
  
  "Wherever you last put it," Caitlin said gently. She imagined him frowning as he looked for it. Soon enough, she heard the soft click of its button, followed by silence as her father presumably read the message.
  
  "Well?" she prodded at last.
  
  "Ah," he said.
  
  "There's a link in the email Doctor Kuroda sent," Caitlin said.
  
  "I see it. Okay, it's clicked. A website is coming up. It says, 'Hello, Miss Caitlin. Please make sure your eyePod is in duplex mode so that it can receive as well as transmit.'"
  
  Caitlin usually carried the eyePod in her left front pocket. She took it out, found the switch, pressed it, and heard the high-pitched beep that meant it was now in the correct mode. "Done," she said.
  
  "Okay," said her dad. "It says, 'Click here to update the software in Miss Caitlin's implant.' Are you ready? It says it might take a long time; apparently it's not a patch but a complete replacement for some of the existing firmware, and the write-to speed for the chip is slow. Do you have to use the restroom?"
  
  "I'm fine," she said. "Besides, we've got Wi-Fi throughout the house."
  
  "Okay," he said. "I'm clicking the link."
  
  The eyePod played a trio of ascending tones, presumably indicating the connection had been established.
  
  Her dad's voice again: "It says, 'Estimated time to completion: forty-one minutes, thirty seconds.' " A pause. "Do you want me to stay?"
  
  Caitlin thought about that. He was fine at reading text off a screen, but it wasn't as though they'd have a conversation if he waited with her. She could have him read something to her to pass the time—catch up on some of her friends' blogs, for instance. But she hardly wanted him looking at that stuff. "Nah. You can go."
  
  She heard him getting up, heard the chair moving against the carpet, heard his footfalls as he headed out the door and down the stairs.
  
  Caitlin lay back with her lower legs sticking straight out over the foot of the bed. She reached around with her right arm, pulled a pillow under her head, and—
  
  Her heart jumped.
  
  An explosion, but silent and not painful. All too quickly it was gone, and—
  
  No. No, it was back: the same loud-but-not-loud, sharp-but-not-sharp sensation, the same …
  
  Gone again, fading from her mind, vanished before she even knew what it was. She got up from the bed, moved over to her desk, and ran her index finger across her Braille display, checking to see if there was an error message. But no: the "Estimated time to completion" clock was still running, the seconds value changing not every second, but rather in jumps of four or five after the appropriate interval had elapsed.
  
  She tipped her head to one side, listening—because that was all she knew how to do—for a repetition of the … the effect that had just occurred. But there was nothing. She stepped to the window, the same one she'd stared out with her blind eyes earlier, and felt for the catch, twisted it, and pushed the wooden frame up, letting the cool evening breeze in. She then turned around, and—
  
  Again, a … a sensation, a something, like bursting, or …
  
  Or flashing.
  
  My God. Caitlin staggered forward, groping with a hand for the edge of the desk. My God, could it be?
  
  There, it happened again: a flash! A flash of …
  
  Light? Could that really be what light was like?
  
  It occurred once more, another—
  
  The words came to her, words she'd read a thousand times before, words that she'd had no idea—now, she understood, as she … God, as she saw for the first time—words that she'd had no conception of what they'd really meant: flashes of light, bursts of light, flickering lights, and—
  
  She staggered some more, found her chair, collapsed into it, the chair rolling on its casters a bit as her weight hit it.
  
  The light wasn't uniform. At first she'd thought it was sometimes bright—its intensity greater, a concept she knew from sound—and sometimes dim. But there was more to it than that. For the light she was seeing now wasn't just dimmer, it was also—
  
  There was nothing else it could be, was there?
  
  She was breathing rapidly, doubly grateful now for the cool air coming in from outside.
  
  The light didn't just vary in brightness but also—
  
  Good God!
  
  But also in color. That had to be it: these different … flavors of light, they were colors!
  
  She thought about calling out to her mother, her father, but she didn't want to do anything that might break the moment, the spell, the magic.
  
  She had no idea which colors she was seeing. Oh, she knew names from her reading, but what they corresponded to she hadn't a clue. But the flashing light she'd just seen was … was darker, somehow, and not just in intensity, than the lights of a moment ago. And—
  
  Jesus! And now there were a few more lights, and they were … were persisting, not flickering, but staying … staying illuminated—that was the word. And it wasn't just a formless light but rather a light with extent, a …
  
  Yes, yes! She'd known intellectually what lines were but she'd never visualized one before. But that's what it had to be: a line, a straight beam of light, and—
  
  And now there were two other beams, crisscrossing it, and their colors—
  
  A word came to her that seemed applicable: the colors contrasted with each other, clashed even.
  
  Colors. And lines. Lines defining—shapes!
  
  Again, concepts she knew but had never visualized: perpendicular lines, parallel lines that—God!—converged at infinity.
  
  Her heart was going to burst. She was seeing!
  
  But what was she seeing? Lines. Colors. Shapes, at least as created by intersecting lines, although she still didn't know what shapes. She'd read about this in preparation for receiving Kuroda's equipment: people gaining sight knew what squares and triangles were conceptually, and by touch, but didn't initially recognize them when they actually saw them.
  
  She was still in the padded chair and, despite all the visual disorientation, had no trouble swinging it to face the window. Her perspective shifted, and she could feel the breeze on her face again, and smell that one of her neighbors was using a fireplace. She knew that the window frame was rectangular, knew that it was divided into a lower and upper square by a crosspiece. Surely she would recognize those simple shapes as she looked at them, and—
  
  But no. No. What she was seeing now was a—what words to use?—a radial pattern, three lines of different colors converging on a single point.
  
  She got up from the chair, moved to the window, and stood before it, grasping one side of the frame in each hand. And then she stared ahead, forcing her concentration onto what must be in front of her. She knew she should be seeing lines perpendicular to the floor and others parallel to it. She knew the frame was twice as tall as the crosspiece.
  
  But what she saw bore no relationship—none!—to what she expected. Instead of anything that resembled the window frame, she was still seeing the radial lines stretching away, and—
  
  Strange. When she moved her head, the view did change, as if she were now looking somewhere else. The center point of all the intersecting lines was now off to one side, and—oh, my!—another such grouping was coming into view on the other side, but the lines didn't seem to correspond to anything in her bedroom.
  
  But wait! It was night now. Yes, the room lights had doubtless been on when her father had been here, but he was serious about saving electricity, forever complaining that Caitlin's mom had left lights on in the kitchen or bathroom— something, fortunately, she never had to worry about being blamed for. He surely would have turned the lights off when he left. (Bashira had said it was creepy that Caitlin's dad did that, but, really, it was sensible … wasn't it?) She couldn't remember hearing the tiny sound of the switch when he left, but he must have used it—and so the room must be dark now, and what she was seeing were just (again a concept she had never experienced) shadows, or something like that.
  
  She turned, her strange view wheeling as she did so. It was disconcerting and disorienting; she'd crossed this room hundreds of times, but she was having trouble walking because of the distraction. Still, the room wasn't that big, and it took only seconds to find the light switch. It was pointing down, but she wasn't sure if that was the position for on or off. She moved it up, and—
  
  Nothing. No change. No new flash of light—nor any dimming of what she was already seeing.
  
  And then she was hit by a thought that should have already occurred to her. Vision was supposed to be at the user's discretion; surely she could shut all this out just by closing her eyes, and—
  
  And nothing.
  
  No difference. The lights, the lines, the colors were all still there. Her heart fell. Whatever she was seeing had no relation to external reality; no wonder she hadn't been able to recognize the window frame. She opened and closed her eyes a couple more times, just to be sure, and flicked the room light on and off (or perhaps off and on!) a few more times, as well.
  
  Caitlin slowly made her way back to her bed and sat on its edge. She'd felt momentarily dizzy as she crossed the room, distracted by the lights, and she lay down, her face pointing up at the ceiling she'd never seen.
  
  She tried to make sense of what she was seeing. If she held her head still, the same part of the image did stay in the … the center. And there was a limit to what she could see—things off to the sides were out of her … her … field of view, that was it. Clearly this bizarre show of lights was behaving like vision, behaving as though it were controlled by her eyes, even if the images she was experiencing didn't have anything to do with what those eyes should be seeing.
  
  Some lines seemed to persist: there was a big one of a darkish color she decided to provisionally call "red," although it almost certainly wasn't that. And another—might as well call it "green"—crossed it near the center of her vision. Those lines seemed to stay put overhead; whenever she directed her eyes toward the ceiling, they were there.
  
  She'd read about people's vision adapting to darkness, so that stars (how she would love to see stars!) slowly became more visible. And although she still didn't know if she was in the dark or in a brightly lit room, as time passed she did seem to be seeing increasing amounts of detail—a finer and more complex filigree of crisscrossing colored lines. But what was causing it? And what did it represent?
  
  She was unused to … what was it now? That phrase she'd read on those websites about vision Kuroda had directed her to, the phrase that was so musical? She frowned, and it came to her: confabulation across saccades. Human eyes swing in continuous arcs when switching from looking at point A to point B, but the brain shuts off the input, perhaps to avoid dizziness, while the eyes are repositioning. Instead of getting swish pans—a term she'd encountered in an article about filmmaking—vision is a series of jump cuts: instantaneous changes from looking at this to looking at that, with the movement of the eye edited out of the conscious experience. The eye normally made several saccades each second: rapid, jerky movements.
  
  The big cross she was seeing now—red in one arm, green in the other—jumped instantaneously in her perception as she moved her eyes, shunting to her peripheral vision (another term finally understood) when she looked away. She did it again and again, flicking back and forth, and—
  
  And suddenly she was plunged into blackness.
  
  Caitlin gasped. She felt as though she were falling, even though she knew she wasn't. The loss of the enigmatic lights was heartbreaking; she'd crawled her way up after fifteen years of deprivation only to be kicked back down into the pit.
  
  Her body sagged against the bedding while she hoped— prayed!—that the lights would return. But, after a full minute, she pulled herself to her feet and walked to her desk, undistracted now by flashes, her paces falling automatically one after another. She touched her Braille display. "Download complete," she read. "Connection closed."
  
  Caitlin felt her heart pounding. Her vision had stopped when the connection via her eyePod between her retinal implant and the Internet had shut down, and—
  
  A crazy thought. Crazy. She turned on her screen reader, and used the tab key to move around the Web page Kuroda had created, listening to snippets of what was written in various locations. But what she wanted wasn't there. Finally, desperately, she hit alt and the left arrow on her keyboard to return to the previous page, and—
  
  Bingo! "Click here to update the software in Miss Caitlin's implant." She could feel her hand shaking as she positioned her index finger above the enter key.
  
  Please, she thought. Let there be light.
  
  She pressed the key.
  
  And there was light.