Speed reader

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <title>Speed reader</title>
    <link rel="stylesheet" href="style.css" />
  </head>
  <body>
    <main class="reader">
      <section class="stage" aria-live="off" title="Click to play or pause">
        <div class="guide" aria-hidden="true"></div>
        <p class="word"><span class="before"></span><span class="focus"></span><span class="after"></span></p>
        <div class="guide" aria-hidden="true"></div>
      </section>

      <div class="bar">
        <button class="play" type="button" aria-label="Play">
          <svg class="icon-play" viewBox="0 0 24 24" aria-hidden="true"><path d="M8 5.5v13l10.5-6.5z" /></svg>
          <svg class="icon-pause" viewBox="0 0 24 24" aria-hidden="true"><path d="M7 5h3.5v14H7zM13.5 5H17v14h-3.5z" /></svg>
        </button>
        <button class="restart" type="button" aria-label="Back to the start">
          <svg viewBox="0 0 24 24" aria-hidden="true"><path d="M5 12a7 7 0 1 0 2.05-4.95M5 4v4h4" /></svg>
        </button>
        <input class="seek" type="range" min="0" max="0" value="0" aria-label="Position" />
        <span class="left">0:00 left</span>
        <label class="speed">
          <input type="range" min="150" max="900" step="25" value="350" aria-label="Words per minute" />
          <output>350 wpm</output>
        </label>
      </div>

      <label class="paste">
        <span class="paste-head"><span>Paste anything</span><span class="count">0 words</span></span>
        <textarea spellcheck="false">This is a speed reader. Every word shows up in the same spot, and one letter stays pinned in red, so your eyes never have to move. Paste anything in here, a long brief, a client email, the terms you were never going to read. Press play, start slow, then nudge the speed up. Most people can read a lot faster than they think.</textarea>
      </label>

      <p class="keys">Space to play · ← → to step · ↑ ↓ for speed</p>
    </main>

    <script src="script.js"></script>
  </body>
</html>

:root {
  --ground: #f4f0ea;
  --ink: #1d1b24;
  --muted: rgba(29, 27, 36, 0.55);
  --line: rgba(29, 27, 36, 0.12);
  --focus: #e5484d;
  --card: rgba(255, 255, 255, 0.72);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100dvh;
  display: grid;
  place-items: center;
  padding: 24px;
  background:
    radial-gradient(50% 40% at 50% 30%, rgba(255, 196, 170, 0.35), transparent 70%),
    radial-gradient(40% 35% at 80% 90%, rgba(185, 160, 255, 0.18), transparent 70%),
    var(--ground);
  color: var(--ink);
  font: 15px/1.45 ui-sans-serif, system-ui, -apple-system, "Segoe UI", sans-serif;
  -webkit-font-smoothing: antialiased;
}

.reader { width: min(720px, 100%); display: grid; gap: 14px; }

/* The word sits in a three-column grid, so the red letter is always in the exact center. */
.stage {
  position: relative;
  display: grid;
  grid-template-rows: 1fr auto 1fr;
  height: 200px;
  padding: 0 28px;
  border-radius: 28px;
  background: var(--card);
  box-shadow: 0 0 0 1px var(--line), 0 30px 60px -36px rgba(60, 40, 30, 0.45);
  cursor: pointer;
  user-select: none;
}

.guide { position: relative; }
.guide::before {
  content: "";
  position: absolute;
  left: 18%;
  right: 18%;
  height: 1px;
  background: var(--line);
}
.guide::after {
  content: "";
  position: absolute;
  left: 50%;
  width: 2px;
  height: 14px;
  margin-left: -1px;
  border-radius: 2px;
  background: var(--focus);
  opacity: 0.55;
}
.guide:first-child::before { bottom: 18px; }
.guide:first-child::after { bottom: 4px; }
.guide:last-child::before { top: 18px; }
.guide:last-child::after { top: 4px; }

.word {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr);
  margin: 0;
  font-size: clamp(34px, 7vw, 58px);
  font-weight: 500;
  letter-spacing: -0.01em;
  line-height: 1.1;
  white-space: pre;
}
.before { text-align: right; }
.focus { color: var(--focus); }

.bar { display: flex; align-items: center; gap: 10px; }

.play, .restart {
  flex: none;
  display: grid;
  place-items: center;
  border: 0;
  border-radius: 50%;
  cursor: pointer;
}
.play { width: 46px; height: 46px; background: var(--ink); color: #fff; }
.play svg { width: 20px; height: 20px; fill: currentColor; }
.play .icon-pause, .reader.is-playing .play .icon-play { display: none; }
.reader.is-playing .play .icon-pause { display: block; }
.restart { width: 38px; height: 38px; background: var(--card); color: var(--ink); box-shadow: 0 0 0 1px var(--line); }
.restart svg { width: 17px; height: 17px; fill: none; stroke: currentColor; stroke-width: 2; stroke-linecap: round; stroke-linejoin: round; }
.play:focus-visible, .restart:focus-visible, textarea:focus-visible { outline: 2px solid var(--focus); outline-offset: 3px; }

input[type="range"] { accent-color: var(--ink); margin: 0; }
.seek { flex: 1; min-width: 60px; }
.left { flex: none; min-width: 64px; font-size: 13px; color: var(--muted); font-variant-numeric: tabular-nums; }
.speed { display: flex; align-items: center; gap: 8px; padding: 6px 12px; border-radius: 999px; background: var(--card); box-shadow: 0 0 0 1px var(--line); }
.speed input { width: 110px; }
.speed output { min-width: 62px; font-size: 13px; font-weight: 500; font-variant-numeric: tabular-nums; }

.paste { display: grid; gap: 6px; transition: opacity 0.3s; }
.reader.is-playing .paste { opacity: 0.45; }
.paste-head { display: flex; justify-content: space-between; font-size: 13px; color: var(--muted); padding: 0 4px; }
textarea {
  width: 100%;
  min-height: 120px;
  padding: 14px 16px;
  border: 0;
  border-radius: 18px;
  background: rgba(255, 255, 255, 0.55);
  box-shadow: 0 0 0 1px var(--line);
  color: var(--ink);
  font: inherit;
  resize: vertical;
}

.keys { margin: 0; text-align: center; font-size: 12.5px; color: var(--muted); }

@media (max-width: 560px) {
  .stage { height: 160px; padding: 0 16px; }
  .bar { flex-wrap: wrap; }
  .speed { order: 5; width: 100%; justify-content: space-between; }
  .speed input { flex: 1; }
  .keys { display: none; }
}

const reader = document.querySelector(".reader");
const stage = document.querySelector(".stage");
const before = document.querySelector(".before");
const focus = document.querySelector(".focus");
const after = document.querySelector(".after");
const playButton = document.querySelector(".play");
const restart = document.querySelector(".restart");
const seek = document.querySelector(".seek");
const left = document.querySelector(".left");
const speed = document.querySelector(".speed input");
const speedOut = document.querySelector(".speed output");
const input = document.querySelector("textarea");
const count = document.querySelector(".count");

let words = [];
let index = 0;
let playing = false;
let wait = 0;
let last = null;

// The letter your eye lands on, a little left of center.
function pivot(letters) {
  const lead = letters.findIndex((ch) => /[\p{L}\p{N}]/u.test(ch));
  const core = letters.filter((ch) => /[\p{L}\p{N}]/u.test(ch)).length;
  const spot = core < 2 ? 0 : core < 6 ? 1 : core < 10 ? 2 : core < 14 ? 3 : 4;
  return Math.min(Math.max(lead, 0) + spot, letters.length - 1);
}

// Linger on punctuation and long words so sentences still breathe.
function pause(word) {
  const beat = 60000 / Number(speed.value);
  if (word.end) return beat * 3;
  if (/[.!?]["')\]]*$/.test(word.text)) return beat * 2.4;
  if (/[,;:—–]["')\]]*$/.test(word.text)) return beat * 1.6;
  return word.text.length > 8 ? beat * 1.3 : beat;
}

function show(i) {
  index = Math.min(Math.max(i, 0), Math.max(words.length - 1, 0));
  const letters = Array.from(words[index]?.text ?? "");
  const at = pivot(letters);
  before.textContent = letters.slice(0, at).join("");
  focus.textContent = letters[at] ?? "";
  after.textContent = letters.slice(at + 1).join("");
  seek.value = String(index);
  const seconds = Math.round(((words.length - index) * 60) / Number(speed.value));
  left.textContent = `${Math.floor(seconds / 60)}:${String(seconds % 60).padStart(2, "0")} left`;
}

function frame(time) {
  requestAnimationFrame(frame);
  if (!playing) return;
  wait -= last === null ? 0 : time - last;
  last = time;
  while (playing && wait <= 0) {
    if (index >= words.length - 1) return setPlaying(false);
    show(index + 1);
    wait += pause(words[index]);
  }
}

function setPlaying(on) {
  playing = on && words.length > 0;
  if (playing) {
    if (index >= words.length - 1) show(0);
    wait = pause(words[index]);
    last = null;
  }
  reader.classList.toggle("is-playing", playing);
  playButton.setAttribute("aria-label", playing ? "Pause" : "Play");
}

function load() {
  words = input.value
    .split(/\n\s*\n/)
    .flatMap((paragraph) => {
      const list = paragraph.split(/\s+/).filter(Boolean).map((text) => ({ text, end: false }));
      if (list.length) list[list.length - 1].end = true;
      return list;
    });
  seek.max = String(Math.max(words.length - 1, 0));
  count.textContent = `${words.length} ${words.length === 1 ? "word" : "words"}`;
  setPlaying(false);
  show(0);
}

function setSpeed(value) {
  speed.value = String(value);
  speedOut.textContent = `${speed.value} wpm`;
  show(index);
}

playButton.addEventListener("click", () => setPlaying(!playing));
stage.addEventListener("click", () => setPlaying(!playing));
restart.addEventListener("click", () => {
  setPlaying(false);
  show(0);
});
seek.addEventListener("input", () => show(Number(seek.value)));
speed.addEventListener("input", () => setSpeed(speed.value));
input.addEventListener("input", load);

document.addEventListener("keydown", (event) => {
  if (event.target.closest("input, textarea, button") || event.metaKey || event.ctrlKey) return;
  const step = { ArrowLeft: -1, ArrowRight: 1 }[event.key];
  if (event.key === " ") setPlaying(!playing);
  else if (step) {
    setPlaying(false);
    show(index + step);
  } else if (event.key === "ArrowUp") setSpeed(Math.min(900, Number(speed.value) + 25));
  else if (event.key === "ArrowDown") setSpeed(Math.max(150, Number(speed.value) - 25));
  else return;
  event.preventDefault();
});

load();
requestAnimationFrame(frame);