High Contrast Toggle

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

:root {
  --bg: #0d1117;
  --surface: #161b22;
  --border: #21262d;
  --text: #e6edf3;
  --text-muted: #8b949e;
  --accent: #6366f1;
  --card-bg: #1c2128;
  --font-size: 14px;
  --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

/* High contrast theme */
[data-theme~="high-contrast"] {
  --bg: #000;
  --surface: #0a0a0a;
  --border: #fff;
  --text: #fff;
  --text-muted: #ddd;
  --accent: #ffff00;
  --card-bg: #111;
}

/* Dyslexia font (simulated with spacing) */
[data-theme~="dyslexia"] {
  --font-family: "Comic Sans MS", "Chalkboard SE", cursive;
  letter-spacing: 0.05em;
  word-spacing: 0.12em;
  line-height: 1.9;
}

/* Large text */
[data-theme~="large-text"] {
  --font-size: 18px;
}

body {
  font-family: var(--font-family);
  font-size: var(--font-size);
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  padding: 32px 16px;
  display: flex;
  justify-content: center;
  transition: background 0.3s, color 0.3s;
}

.demo {
  width: 100%;
  max-width: 620px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

/* Settings bar */
.settings-bar {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 18px;
  transition: background 0.3s, border-color 0.3s;
}

.settings-title {
  font-size: 15px;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 16px;
}

.settings-grid {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.setting-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.setting-info {
  display: flex;
  flex-direction: column;
  gap: 2px;
}
.setting-label {
  font-size: var(--font-size);
  font-weight: 600;
  color: var(--text);
}
.setting-desc {
  font-size: 12px;
  color: var(--text-muted);
}

/* Toggle switch */
.toggle-switch {
  width: 48px;
  height: 26px;
  background: var(--border);
  border: 2px solid var(--border);
  border-radius: 13px;
  cursor: pointer;
  position: relative;
  flex-shrink: 0;
  transition: background 0.2s, border-color 0.2s;
}
.toggle-switch[aria-checked="true"] {
  background: var(--accent);
  border-color: var(--accent);
}
.toggle-switch:focus-visible {
  outline: 2.5px solid var(--accent);
  outline-offset: 2px;
}

.toggle-knob {
  position: absolute;
  top: 3px;
  left: 3px;
  width: 16px;
  height: 16px;
  background: #fff;
  border-radius: 50%;
  transition: transform 0.2s;
}
.toggle-switch[aria-checked="true"] .toggle-knob {
  transform: translateX(22px);
}

/* Preview area */
.preview-area {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 20px;
  display: flex;
  flex-direction: column;
  gap: 14px;
  transition: all 0.3s;
}

.preview-heading {
  font-size: 16px;
  font-weight: 700;
  color: var(--text);
}
.preview-text {
  font-size: var(--font-size);
  color: var(--text);
  line-height: 1.7;
}

.preview-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 14px 16px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.preview-card-title {
  font-size: var(--font-size);
  font-weight: 700;
  color: var(--text);
}
.preview-card-body {
  font-size: 13px;
  color: var(--text-muted);
  line-height: 1.6;
}

.preview-btn {
  align-self: flex-start;
  padding: 8px 18px;
  background: var(--accent);
  color: var(--bg);
  border: 2px solid var(--accent);
  border-radius: 8px;
  font-size: 13px;
  font-weight: 700;
  cursor: pointer;
  transition: opacity 0.15s;
}
.preview-btn:hover {
  opacity: 0.85;
}

.preview-link {
  color: var(--accent);
  font-size: var(--font-size);
  font-weight: 600;
  text-decoration: underline;
}

const html = document.documentElement;

function getThemes() {
  return new Set(html.dataset.theme.trim().split(/\s+/).filter(Boolean));
}

function setTheme(themes) {
  html.dataset.theme = [...themes].join(" ") || "default";
}

function bindToggle(id, themeName) {
  const btn = document.getElementById(id);
  btn.addEventListener("click", () => {
    const themes = getThemes();
    themes.delete("default");
    if (themes.has(themeName)) {
      themes.delete(themeName);
      btn.setAttribute("aria-checked", "false");
    } else {
      themes.add(themeName);
      btn.setAttribute("aria-checked", "true");
    }
    if (themes.size === 0) themes.add("default");
    setTheme(themes);
  });
}

bindToggle("contrastToggle", "high-contrast");
bindToggle("dyslexiaToggle", "dyslexia");
bindToggle("largeTextToggle", "large-text");

// Persist to sessionStorage
const stored = sessionStorage.getItem("a11y-theme");
if (stored) {
  const themes = new Set(stored.split(" ").filter(Boolean));
  setTheme(themes);
  themes.forEach((t) => {
    const map = {
      "high-contrast": "contrastToggle",
      dyslexia: "dyslexiaToggle",
      "large-text": "largeTextToggle",
    };
    if (map[t]) document.getElementById(map[t]).setAttribute("aria-checked", "true");
  });
}

const observer = new MutationObserver(() => {
  sessionStorage.setItem("a11y-theme", html.dataset.theme);
});
observer.observe(html, { attributes: true, attributeFilter: ["data-theme"] });

<!DOCTYPE html>
<html lang="en" data-theme="default">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>High Contrast Toggle</title>
  <link rel="stylesheet" href="style.css" />
</head>
<body>
<div class="demo">
  <div class="settings-bar">
    <h2 class="settings-title">Accessibility Settings</h2>
    <div class="settings-grid">

      <div class="setting-item">
        <div class="setting-info">
          <span class="setting-label">High Contrast</span>
          <span class="setting-desc">Increase contrast for better readability</span>
        </div>
        <button class="toggle-switch" id="contrastToggle" role="switch" aria-checked="false" aria-label="Toggle high contrast">
          <span class="toggle-knob"></span>
        </button>
      </div>

      <div class="setting-item">
        <div class="setting-info">
          <span class="setting-label">Dyslexia Font</span>
          <span class="setting-desc">Use OpenDyslexic-style font spacing</span>
        </div>
        <button class="toggle-switch" id="dyslexiaToggle" role="switch" aria-checked="false" aria-label="Toggle dyslexia font">
          <span class="toggle-knob"></span>
        </button>
      </div>

      <div class="setting-item">
        <div class="setting-info">
          <span class="setting-label">Large Text</span>
          <span class="setting-desc">Increase base font size</span>
        </div>
        <button class="toggle-switch" id="largeTextToggle" role="switch" aria-checked="false" aria-label="Toggle large text">
          <span class="toggle-knob"></span>
        </button>
      </div>

    </div>
  </div>

  <div class="preview-area" id="previewArea">
    <h3 class="preview-heading">Preview Area</h3>
    <p class="preview-text">The quick brown fox jumps over the lazy dog. This text demonstrates how the accessibility settings affect readability. Toggle the options above to see how the content adapts.</p>
    <div class="preview-card">
      <p class="preview-card-title">Sample Content Card</p>
      <p class="preview-card-body">This card shows how interactive elements and backgrounds change with different accessibility modes.</p>
      <button class="preview-btn">Action Button</button>
    </div>
    <a href="#" class="preview-link">A sample hyperlink →</a>
  </div>
</div>
<script src="script.js"></script>
</body>
</html>