High Contrast Theme

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

/* ── Normal theme (default) ── */
:root {
  --bg: #0a0a0a;
  --bg-surface: #141414;
  --bg-elevated: #1a1a1a;
  --border: #262626;
  --text-primary: #e5e5e5;
  --text-secondary: #a3a3a3;
  --text-muted: #737373;
  --accent: #3b82f6;
  --accent-hover: #2563eb;
  --positive: #22c55e;
  --negative: #ef4444;
  --warning: #f59e0b;
  --info: #3b82f6;
  --link: #60a5fa;
  --focus-ring: #3b82f6;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.3);
  --btn-primary-bg: #3b82f6;
  --btn-primary-text: #ffffff;
  --btn-secondary-bg: transparent;
  --btn-secondary-text: #e5e5e5;
  --btn-secondary-border: #404040;
  --btn-danger-bg: #dc2626;
  --btn-danger-text: #ffffff;
  --input-bg: #171717;
  --input-border: #333333;
  --input-text: #e5e5e5;
}

/* ── High contrast theme ── */
.high-contrast {
  --bg: #000000;
  --bg-surface: #000000;
  --bg-elevated: #000000;
  --border: #ffffff;
  --text-primary: #ffffff;
  --text-secondary: #ffffff;
  --text-muted: #ffffff;
  --accent: #ffff00;
  --accent-hover: #ffff00;
  --positive: #00ff00;
  --negative: #ff0000;
  --warning: #ffff00;
  --info: #00ffff;
  --link: #ffff00;
  --focus-ring: #ffffff;
  --shadow: none;
  --btn-primary-bg: #ffff00;
  --btn-primary-text: #000000;
  --btn-secondary-bg: #000000;
  --btn-secondary-text: #ffffff;
  --btn-secondary-border: #ffffff;
  --btn-danger-bg: #ff0000;
  --btn-danger-text: #ffffff;
  --input-bg: #000000;
  --input-border: #ffffff;
  --input-text: #ffffff;
}

.high-contrast .card,
.high-contrast .alert,
.high-contrast .nav,
.high-contrast .form-section {
  border-width: 2px;
}

.high-contrast .btn {
  border-width: 2px;
  font-weight: 700;
}
.high-contrast input,
.high-contrast select {
  border-width: 2px;
}

/* ── Forced-colors simulation ── */
.forced-colors {
  --bg: Canvas;
  --bg-surface: Canvas;
  --bg-elevated: Canvas;
  --border: CanvasText;
  --text-primary: CanvasText;
  --text-secondary: CanvasText;
  --text-muted: GrayText;
  --accent: LinkText;
  --accent-hover: ActiveText;
  --positive: CanvasText;
  --negative: CanvasText;
  --warning: CanvasText;
  --info: CanvasText;
  --link: LinkText;
  --focus-ring: Highlight;
  --shadow: none;
  --btn-primary-bg: ButtonFace;
  --btn-primary-text: ButtonText;
  --btn-secondary-bg: ButtonFace;
  --btn-secondary-text: ButtonText;
  --btn-secondary-border: ButtonText;
  --btn-danger-bg: ButtonFace;
  --btn-danger-text: ButtonText;
  --input-bg: Field;
  --input-border: FieldText;
  --input-text: FieldText;
}

.forced-colors .card,
.forced-colors .alert,
.forced-colors .nav,
.forced-colors .form-section {
  border-width: 2px;
  box-shadow: none;
}

.forced-colors .btn {
  border: 2px solid ButtonText;
}
.forced-colors .card-change {
  font-weight: 700;
  text-decoration: underline;
}

/* ── Respond to real OS preferences ── */
@media (prefers-contrast: more) {
  :root {
    --border: #ffffff;
    --text-muted: #d4d4d4;
    --shadow: none;
  }
  .card,
  .alert,
  .nav,
  .form-section {
    border-width: 2px;
  }
  .btn {
    border-width: 2px;
  }
}

@media (forced-colors: active) {
  .card,
  .alert,
  .btn,
  .nav,
  input,
  select {
    border: 2px solid ButtonText;
  }
  .card-change.positive::before,
  .card-change.negative::before {
    font-weight: 700;
  }
}

/* ── Layout ── */
body {
  font-family: Inter, system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text-primary);
  min-height: 100vh;
  display: flex;
  justify-content: center;
  padding: 2rem;
  transition: background 0.25s, color 0.25s;
}

.page {
  width: 100%;
  max-width: 720px;
}

.header {
  margin-bottom: 1.5rem;
}
.header-title {
  font-size: 1.75rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 0.375rem;
}
.header-sub {
  color: var(--text-muted);
  font-size: 0.875rem;
  margin-bottom: 1rem;
}

/* ── Theme toggle ── */
.theme-toggle {
  display: inline-flex;
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 0.5rem;
  overflow: hidden;
}

.toggle-btn {
  background: none;
  border: none;
  color: var(--text-secondary);
  padding: 0.5rem 1rem;
  font-size: 0.8125rem;
  font-weight: 500;
  cursor: pointer;
  transition: background 0.15s, color 0.15s;
}

.toggle-btn:hover {
  background: var(--bg-elevated);
}
.toggle-btn.active {
  background: var(--accent);
  color: var(--btn-primary-text);
  font-weight: 700;
}

/* ── Nav ── */
.nav {
  display: flex;
  gap: 0.25rem;
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  padding: 0.375rem;
  margin-bottom: 1.5rem;
  box-shadow: var(--shadow);
}

.nav-link {
  color: var(--text-secondary);
  text-decoration: none;
  padding: 0.5rem 1rem;
  border-radius: 0.5rem;
  font-size: 0.8125rem;
  font-weight: 500;
  transition: background 0.15s, color 0.15s;
}

.nav-link:hover {
  background: var(--bg-elevated);
  color: var(--text-primary);
}
.nav-link.active {
  background: var(--bg-elevated);
  color: var(--text-primary);
  font-weight: 600;
}

/* ── Cards ── */
.cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.75rem;
  margin-bottom: 1.5rem;
}

.card {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  padding: 1.25rem;
  box-shadow: var(--shadow);
}

.card-title {
  font-size: 0.75rem;
  color: var(--text-muted);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.5rem;
}
.card-value {
  font-size: 1.5rem;
  font-weight: 800;
  margin-bottom: 0.375rem;
}
.card-change {
  font-size: 0.75rem;
}
.card-change.positive {
  color: var(--positive);
}
.card-change.negative {
  color: var(--negative);
}

/* ── Form ── */
.form-section {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  padding: 1.5rem;
  margin-bottom: 1.5rem;
  box-shadow: var(--shadow);
}

.section-title {
  font-size: 1rem;
  font-weight: 700;
  margin-bottom: 1rem;
}

.form-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  margin-bottom: 1.25rem;
}

.form-group label {
  display: block;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 0.375rem;
}

.form-group input[type="text"],
.form-group input[type="email"],
.form-group select {
  width: 100%;
  background: var(--input-bg);
  border: 1px solid var(--input-border);
  border-radius: 0.5rem;
  color: var(--input-text);
  padding: 0.5rem 0.75rem;
  font-size: 0.875rem;
  outline: none;
  transition: border-color 0.15s;
}

.form-group input:focus,
.form-group select:focus {
  border-color: var(--focus-ring);
}

.checkbox-group {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  justify-content: flex-end;
}
.checkbox-label {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.8125rem;
  cursor: pointer;
  color: var(--text-secondary);
}

.checkbox-label input[type="checkbox"] {
  width: 16px;
  height: 16px;
  accent-color: var(--accent);
}

.form-actions {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
}

.btn {
  padding: 0.5rem 1rem;
  border-radius: 0.5rem;
  font-size: 0.8125rem;
  font-weight: 600;
  cursor: pointer;
  border: 1px solid transparent;
  transition: background 0.15s, border-color 0.15s;
}

.btn-primary {
  background: var(--btn-primary-bg);
  color: var(--btn-primary-text);
}
.btn-primary:hover {
  opacity: 0.9;
}
.btn-secondary {
  background: var(--btn-secondary-bg);
  color: var(--btn-secondary-text);
  border-color: var(--btn-secondary-border);
}
.btn-secondary:hover {
  background: var(--bg-elevated);
}
.btn-danger {
  background: var(--btn-danger-bg);
  color: var(--btn-danger-text);
}
.btn-danger:hover {
  opacity: 0.9;
}

/* ── Alerts ── */
.alerts {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  margin-bottom: 1.5rem;
}

.alert {
  padding: 0.875rem 1rem;
  border-radius: 0.5rem;
  font-size: 0.8125rem;
  line-height: 1.5;
  border: 1px solid var(--border);
}

.alert-info {
  background: color-mix(in srgb, var(--info) 10%, var(--bg-surface));
  border-left: 3px solid var(--info);
}
.alert-warning {
  background: color-mix(in srgb, var(--warning) 10%, var(--bg-surface));
  border-left: 3px solid var(--warning);
}
.alert-error {
  background: color-mix(in srgb, var(--negative) 10%, var(--bg-surface));
  border-left: 3px solid var(--negative);
}

/* ── Links section ── */
.links-section {
  margin-bottom: 2rem;
}
.links-section .section-title {
  margin-bottom: 0.75rem;
}

.body-text {
  font-size: 0.9375rem;
  line-height: 1.7;
  color: var(--text-secondary);
}

.body-text a {
  color: var(--link);
  text-decoration: underline;
  text-underline-offset: 2px;
}
.body-text a:hover {
  color: var(--accent-hover);
}

@media (max-width: 600px) {
  body {
    padding: 1rem;
  }
  .page {
    max-width: 100%;
  }

  .header-title {
    font-size: 1.35rem;
  }
  .header-sub {
    font-size: 0.8rem;
  }

  /* Theme toggle wraps */
  .theme-toggle {
    display: flex;
    width: 100%;
  }

  .toggle-btn {
    flex: 1;
    padding: 0.5rem 0.5rem;
    font-size: 0.75rem;
    text-align: center;
  }

  /* Nav scrolls horizontally */
  .nav {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
    flex-wrap: nowrap;
  }

  .nav::-webkit-scrollbar {
    display: none;
  }

  .nav-link {
    white-space: nowrap;
    flex-shrink: 0;
    font-size: 0.78rem;
    padding: 0.5rem 0.75rem;
  }

  /* Cards single column */
  .cards {
    grid-template-columns: 1fr;
  }

  .card {
    padding: 1rem;
  }
  .card-value {
    font-size: 1.25rem;
  }

  /* Form */
  .form-section {
    padding: 1rem;
  }
  .form-grid {
    grid-template-columns: 1fr;
  }
  .form-actions {
    flex-direction: column;
  }
  .btn {
    width: 100%;
    text-align: center;
  }

  /* Alerts */
  .alert {
    font-size: 0.78rem;
    padding: 0.75rem;
  }

  .section-title {
    font-size: 0.9rem;
  }
  .body-text {
    font-size: 0.85rem;
  }
}

(function () {
  var buttons = document.querySelectorAll(".toggle-btn");
  var body = document.body;

  var modes = {
    normal: "",
    "high-contrast": "high-contrast",
    "forced-colors": "forced-colors",
  };

  function setMode(mode) {
    // Remove all mode classes
    body.classList.remove("high-contrast", "forced-colors");

    // Add selected mode class
    if (modes[mode]) {
      body.classList.add(modes[mode]);
    }

    // Update button states
    buttons.forEach(function (btn) {
      var isActive = btn.getAttribute("data-mode") === mode;
      btn.classList.toggle("active", isActive);
      btn.setAttribute("aria-pressed", isActive ? "true" : "false");
    });
  }

  // Attach click handlers
  buttons.forEach(function (btn) {
    btn.addEventListener("click", function () {
      setMode(btn.getAttribute("data-mode"));
    });
  });

  // Keyboard support for toggle group
  var toggleGroup = document.querySelector(".theme-toggle");
  toggleGroup.addEventListener("keydown", function (e) {
    var current = document.querySelector(".toggle-btn.active");
    var btns = Array.from(buttons);
    var idx = btns.indexOf(current);

    if (e.key === "ArrowRight" || e.key === "ArrowDown") {
      e.preventDefault();
      var next = btns[(idx + 1) % btns.length];
      next.focus();
      setMode(next.getAttribute("data-mode"));
    } else if (e.key === "ArrowLeft" || e.key === "ArrowUp") {
      e.preventDefault();
      var prev = btns[(idx - 1 + btns.length) % btns.length];
      prev.focus();
      setMode(prev.getAttribute("data-mode"));
    }
  });
})();

<!doctype html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>High Contrast Theme</title>
  <link rel="stylesheet" href="style.css" />
</head>
<body>
  <div class="page">
    <header class="header">
      <h1 class="header-title">High Contrast Theme</h1>
      <p class="header-sub">Toggle between normal, high-contrast, and forced-colors simulation.</p>
      <div class="theme-toggle" role="radiogroup" aria-label="Theme mode">
        <button class="toggle-btn active" data-mode="normal" aria-pressed="true">Normal</button>
        <button class="toggle-btn" data-mode="high-contrast" aria-pressed="false">High Contrast</button>
        <button class="toggle-btn" data-mode="forced-colors" aria-pressed="false">Forced Colors</button>
      </div>
    </header>

    <!-- Navigation -->
    <nav class="nav" aria-label="Main navigation">
      <a href="#" class="nav-link active" onclick="return false">Dashboard</a>
      <a href="#" class="nav-link" onclick="return false">Projects</a>
      <a href="#" class="nav-link" onclick="return false">Settings</a>
      <a href="#" class="nav-link" onclick="return false">Help</a>
    </nav>

    <!-- Cards -->
    <div class="cards">
      <div class="card">
        <h2 class="card-title">Active Users</h2>
        <p class="card-value">12,847</p>
        <p class="card-change positive">+14.2% from last month</p>
      </div>
      <div class="card">
        <h2 class="card-title">Revenue</h2>
        <p class="card-value">$48,290</p>
        <p class="card-change positive">+8.7% from last month</p>
      </div>
      <div class="card">
        <h2 class="card-title">Bounce Rate</h2>
        <p class="card-value">23.4%</p>
        <p class="card-change negative">+2.1% from last month</p>
      </div>
    </div>

    <!-- Form elements -->
    <div class="form-section">
      <h2 class="section-title">Form Elements</h2>
      <div class="form-grid">
        <div class="form-group">
          <label for="name-input">Full Name</label>
          <input type="text" id="name-input" value="Jane Doe" />
        </div>
        <div class="form-group">
          <label for="email-input">Email</label>
          <input type="email" id="email-input" value="jane@example.com" />
        </div>
        <div class="form-group">
          <label for="role-select">Role</label>
          <select id="role-select">
            <option>Admin</option>
            <option selected>Editor</option>
            <option>Viewer</option>
          </select>
        </div>
        <div class="form-group checkbox-group">
          <label class="checkbox-label">
            <input type="checkbox" checked />
            <span>Enable notifications</span>
          </label>
          <label class="checkbox-label">
            <input type="checkbox" />
            <span>Enable dark mode</span>
          </label>
        </div>
      </div>
      <div class="form-actions">
        <button class="btn btn-primary">Save Changes</button>
        <button class="btn btn-secondary">Cancel</button>
        <button class="btn btn-danger">Delete Account</button>
      </div>
    </div>

    <!-- Alerts -->
    <div class="alerts">
      <div class="alert alert-info" role="alert">
        <strong>Info:</strong> Your subscription renews on April 15.
      </div>
      <div class="alert alert-warning" role="alert">
        <strong>Warning:</strong> Storage is at 85% capacity.
      </div>
      <div class="alert alert-error" role="alert">
        <strong>Error:</strong> Payment method expired. Please update.
      </div>
    </div>

    <!-- Links -->
    <div class="links-section">
      <h2 class="section-title">Links &amp; Text</h2>
      <p class="body-text">
        This paragraph contains <a href="#" onclick="return false">inline links</a> that should remain
        clearly distinguishable in all contrast modes. The
        <a href="#" onclick="return false">high contrast theme</a> uses bold borders and removes
        subtle shadows. <a href="#" onclick="return false">Forced colors mode</a> maps all colors
        to system keywords.
      </p>
    </div>
  </div>
  <script src="script.js"></script>
</body>
</html>