Theme Transition

Dark/light theme toggle with circular clip-path wipe powered by the View Transitions API.

view-transitions-api clip-path

Targets: JS HTML

Code

*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

/* ── Theme tokens ── */
[data-theme="dark"] {
  --bg: #070a12;
  --bg-elevated: #121a2b;
  --border: #263249;
  --text: #f0f4fb;
  --text-secondary: #8a95a8;
  --accent: #86e8ff;
  --secondary: #ae52ff;
  --tertiary: #ff40d6;
  --code-bg: rgba(134, 232, 255, 0.1);
  --code-color: #86e8ff;
  --card-shadow: rgba(0, 0, 0, 0.3);
}

[data-theme="light"] {
  --bg: #f5f7fb;
  --bg-elevated: #ffffff;
  --border: #dce3ed;
  --text: #1a1f2e;
  --text-secondary: #5a6478;
  --accent: #0077cc;
  --secondary: #7c3aed;
  --tertiary: #db2777;
  --code-bg: rgba(0, 119, 204, 0.08);
  --code-color: #0077cc;
  --card-shadow: rgba(0, 0, 0, 0.06);
}

html {
  font-family: "Inter", "SF Pro Display", system-ui, sans-serif;
}

body {
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  transition: none; /* transitions handled by View Transitions API */
}

/* ── Page ── */
.page {
  max-width: 880px;
  margin: 0 auto;
  padding: 5rem 2rem 4rem;
}

.header {
  text-align: center;
  margin-bottom: 2.5rem;
}

.eyebrow {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.18em;
  color: var(--accent);
  margin-bottom: 1rem;
}

h1 {
  font-size: clamp(2rem, 5vw, 3.5rem);
  font-weight: 700;
  letter-spacing: -0.02em;
}

.subtitle {
  font-size: clamp(0.9rem, 2vw, 1.05rem);
  color: var(--text-secondary);
  max-width: 500px;
  margin: 0.75rem auto 0;
  line-height: 1.6;
}

/* ── Toggle button ── */
.toggle-area {
  display: flex;
  justify-content: center;
  margin-bottom: 3rem;
}

.theme-toggle {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.75rem 1.5rem;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 999px;
  color: var(--text);
  font: 600 0.85rem / 1 "Inter", system-ui, sans-serif;
  cursor: pointer;
  transition: border-color 0.2s, box-shadow 0.2s;
}

.theme-toggle:hover {
  border-color: var(--accent);
  box-shadow: 0 0 16px rgba(0, 0, 0, 0.1);
}

.toggle-icon {
  display: flex;
  align-items: center;
  color: var(--accent);
}

[data-theme="dark"] .icon-moon {
  display: none;
}
[data-theme="light"] .icon-sun {
  display: none;
}

/* ── Cards ── */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1rem;
  margin-bottom: 2.5rem;
}

.demo-card {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 1.5rem;
  box-shadow: 0 2px 12px var(--card-shadow);
}

.card-header {
  display: flex;
  gap: 0.4rem;
  margin-bottom: 1rem;
}

.card-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--dot-color);
}

.demo-card h3 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
}

.demo-card p {
  font-size: 0.85rem;
  color: var(--text-secondary);
  line-height: 1.5;
}

code {
  background: var(--code-bg);
  color: var(--code-color);
  padding: 0.12rem 0.4rem;
  border-radius: 4px;
  font-size: 0.8rem;
}

/* ── Sample text ── */
.sample-text {
  margin-bottom: 2.5rem;
}

.sample-text h2 {
  font-size: clamp(1.5rem, 3vw, 2.2rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 1rem;
}

.sample-text p {
  font-size: 0.95rem;
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: 1rem;
}

/* ── Back button ── */
.btn-back {
  display: inline-block;
  padding: 0.7rem 2rem;
  border-radius: 999px;
  border: 1px solid var(--border);
  color: var(--accent);
  text-decoration: none;
  font: 600 0.85rem / 1 "Inter", system-ui, sans-serif;
  transition: border-color 0.25s, background 0.25s;
}

.btn-back:hover {
  background: var(--bg-elevated);
  border-color: var(--accent);
}

/* ══════════════════════════════════════════
   View Transition: Circular clip-path wipe
   ══════════════════════════════════════════ */

::view-transition-old(root),
::view-transition-new(root) {
  animation: none;
  mix-blend-mode: normal;
}

/* Old snapshot fades, new snapshot clips in */
::view-transition-old(root) {
  z-index: 1;
}

::view-transition-new(root) {
  z-index: 9999;
  animation: clip-reveal 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}

@keyframes clip-reveal {
  from {
    clip-path: circle(0% at var(--click-x, 50%) var(--click-y, 50%));
  }
  to {
    clip-path: circle(150% at var(--click-x, 50%) var(--click-y, 50%));
  }
}

/* ── Fallback for no View Transitions ── */
.no-vt body {
  transition: background 0.3s ease, color 0.3s ease;
}

@media (max-width: 640px) {
  .page {
    padding: 3rem 1rem 3rem;
  }
  .card-grid {
    grid-template-columns: 1fr;
  }
}

if (!window.MotionPreference) {
  const __mql = window.matchMedia("(prefers-reduced-motion: reduce)");
  const __listeners = new Set();

  const MotionPreference = {
    prefersReducedMotion() {
      return __mql.matches;
    },
    setOverride(value) {
      const reduced = Boolean(value);
      document.documentElement.classList.toggle("reduced-motion", reduced);
      window.dispatchEvent(new CustomEvent("motion-preference", { detail: { reduced } }));
      for (const listener of __listeners) {
        try {
          listener({ reduced, override: reduced, systemReduced: __mql.matches });
        } catch {}
      }
    },
    onChange(listener) {
      __listeners.add(listener);
      try {
        listener({
          reduced: __mql.matches,
          override: null,
          systemReduced: __mql.matches,
        });
      } catch {}
      return () => __listeners.delete(listener);
    },
    getState() {
      return { reduced: __mql.matches, override: null, systemReduced: __mql.matches };
    },
  };

  window.MotionPreference = MotionPreference;
}

function prefersReducedMotion() {
  return window.MotionPreference.prefersReducedMotion();
}

function initDemoShell() {
  // No-op shim in imported standalone snippets.
}

// ── Demo shell ──
initDemoShell({
  title: "Theme Transition",
  category: "transitions",
  tech: ["view-transitions-api", "clip-path"],
});

// ── Check support ──
const supportsVT = typeof document.startViewTransition === "function";
if (!supportsVT) document.body.classList.add("no-vt");

// ── Refs ──
const root = document.documentElement;
const toggle = document.getElementById("theme-toggle");
const label = document.getElementById("toggle-label");

function getCurrentTheme() {
  return root.getAttribute("data-theme") || "dark";
}

function updateLabel() {
  const theme = getCurrentTheme();
  label.textContent = theme === "dark" ? "Switch to Light" : "Switch to Dark";
}

// ── Toggle handler ──
toggle.addEventListener("click", (e) => {
  const nextTheme = getCurrentTheme() === "dark" ? "light" : "dark";

  // Set CSS custom properties for click position (used in clip-path animation)
  const rect = toggle.getBoundingClientRect();
  const x = rect.left + rect.width / 2;
  const y = rect.top + rect.height / 2;
  root.style.setProperty("--click-x", `${x}px`);
  root.style.setProperty("--click-y", `${y}px`);

  const applyTheme = () => {
    root.setAttribute("data-theme", nextTheme);
    updateLabel();
  };

  if (supportsVT && !prefersReducedMotion()) {
    const transition = document.startViewTransition(applyTheme);
  } else {
    applyTheme();
  }
});

// ── Init ──
updateLabel();

<!DOCTYPE html>
<html lang="en" data-theme="dark">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Theme Transition — stealthisdesign</title>
  <link rel="stylesheet" href="style.css">
  </head>
<body>
  <main class="page">
    <header class="header">
      <span class="eyebrow">Demo 13</span>
      <h1>Theme Transition</h1>
      <p class="subtitle">Click the toggle below to switch themes with a circular clip-path wipe powered by the View Transitions API.</p>
    </header>

    <div class="toggle-area">
      <button id="theme-toggle" class="theme-toggle" aria-label="Toggle theme">
        <span class="toggle-icon" id="toggle-icon">
          <svg class="icon-sun" width="22" height="22" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round">
            <circle cx="12" cy="12" r="5"/>
            <line x1="12" y1="1" x2="12" y2="3"/>
            <line x1="12" y1="21" x2="12" y2="23"/>
            <line x1="4.22" y1="4.22" x2="5.64" y2="5.64"/>
            <line x1="18.36" y1="18.36" x2="19.78" y2="19.78"/>
            <line x1="1" y1="12" x2="3" y2="12"/>
            <line x1="21" y1="12" x2="23" y2="12"/>
            <line x1="4.22" y1="19.78" x2="5.64" y2="18.36"/>
            <line x1="18.36" y1="5.64" x2="19.78" y2="4.22"/>
          </svg>
          <svg class="icon-moon" width="22" height="22" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round">
            <path d="M21 12.79A9 9 0 1 1 11.21 3 7 7 0 0 0 21 12.79z"/>
          </svg>
        </span>
        <span class="toggle-label" id="toggle-label">Switch to Light</span>
      </button>
    </div>

    <section class="demo-content">
      <div class="card-grid">
        <div class="demo-card">
          <div class="card-header">
            <span class="card-dot" style="--dot-color: var(--accent);"></span>
            <span class="card-dot" style="--dot-color: var(--secondary);"></span>
            <span class="card-dot" style="--dot-color: var(--tertiary);"></span>
          </div>
          <h3>View Transitions API</h3>
          <p>The <code>document.startViewTransition()</code> method captures before/after snapshots and animates between them using CSS pseudo-elements.</p>
        </div>
        <div class="demo-card">
          <div class="card-header">
            <span class="card-dot" style="--dot-color: var(--accent);"></span>
            <span class="card-dot" style="--dot-color: var(--secondary);"></span>
            <span class="card-dot" style="--dot-color: var(--tertiary);"></span>
          </div>
          <h3>Circular Wipe</h3>
          <p>A custom <code>::view-transition-new(root)</code> animation uses <code>clip-path: circle()</code> expanding from the toggle button position.</p>
        </div>
        <div class="demo-card">
          <div class="card-header">
            <span class="card-dot" style="--dot-color: var(--accent);"></span>
            <span class="card-dot" style="--dot-color: var(--secondary);"></span>
            <span class="card-dot" style="--dot-color: var(--tertiary);"></span>
          </div>
          <h3>CSS Custom Properties</h3>
          <p>Theme colors are defined as CSS variables on <code>[data-theme]</code>. The transition swaps theme by toggling this attribute.</p>
        </div>
      </div>

      <div class="sample-text">
        <h2>The Art of Transitions</h2>
        <p>A well-crafted theme transition doesn't just swap colors — it tells a story. The circular wipe radiates from the point of interaction, creating a clear cause-and-effect relationship that feels natural and intentional.</p>
        <p>Without the View Transitions API, achieving this effect would require complex overlay management, clipping containers, and careful z-index choreography. With it, the browser handles the heavy lifting.</p>
      </div>
    </section>

    <a href="/" class="btn-back">Back to Showcase</a>
  </main>

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

Theme Transition

Dark/light theme toggle with circular clip-path wipe powered by the View Transitions API.

Source

Repository: libs-genclaude
Original demo id: 13-theme-transition

Notes

Dark/light theme toggle with circular clip-path wipe powered by the View Transitions API.