:root {
    --bg: #FBF1E6;
    --bg-glow: #F6E4CF;
    --text: #4A3B32;
    --text-soft: #8A7A6D;
    --circle: #2F8F5B;
    --circle-dark: #1F6E45;
    --circle-shadow: rgba(47, 143, 91, 0.32);
    --card-shadow: rgba(120, 90, 60, 0.12);
    --card-bg: #ffffffb0;
    --card-border: rgba(74, 59, 50, 0.10);
    --toggle-bg: #ffffffaa;
    --toggle-border: rgba(74, 59, 50, 0.12);
    --transition: 0.4s cubic-bezier(0.4, 0, 0.2, 1);
  }

  [data-theme="dark"] {
    --bg: #241C17;
    --bg-glow: #362A21;
    --text: #F3E8DC;
    --text-soft: #B4A392;
    --circle: #4CAF7D;
    --circle-dark: #2E8F5C;
    --circle-shadow: rgba(76, 175, 125, 0.42);
    --card-shadow: rgba(0, 0, 0, 0.35);
    --card-bg: #ffffff0f;
    --card-border: rgba(255, 255, 255, 0.10);
    --toggle-bg: #ffffff14;
    --toggle-border: rgba(255, 255, 255, 0.14);
  }

  * { box-sizing: border-box; }
  html, body { height: 100%; margin: 0; touch-action: manipulation; }

  body {
    font-family: 'Playpen Sans', sans-serif;
    background:
      radial-gradient(circle at 20% 15%, var(--bg-glow), transparent 55%),
      radial-gradient(circle at 85% 90%, var(--bg-glow), transparent 50%),
      var(--bg);
    background-attachment: fixed;
    background-size: cover;
    color: var(--text);
    min-height: 100vh;
    transition: background var(--transition), color var(--transition);
  }

  .page {
    min-height: 100vh;
    display: flex;
    justify-content: center;
    padding: calc(90px + env(safe-area-inset-top)) 20px calc(50px + env(safe-area-inset-bottom));
  }

  .wrap {
    width: 100%;
    max-width: 520px;
    display: flex;
    flex-direction: column;
    gap: 20px;
  }

  /* ---------- top icons ---------- */
  .icon-btn {
    position: fixed;
    top: max(24px, env(safe-area-inset-top));
    width: 48px;
    height: 48px;
    border-radius: 50%;
    border: 1px solid var(--toggle-border);
    background: var(--toggle-bg);
    backdrop-filter: blur(6px);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    text-decoration: none;
    transition: background var(--transition), border-color var(--transition), transform 0.2s ease;
    z-index: 20;
  }
  .icon-btn:hover { transform: scale(1.06); }
  .icon-btn svg { width: 21px; height: 21px; stroke: var(--text); }

  #themeToggle { right: 24px; }
  #backBtn { left: 24px; }

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

  /* ---------- page header ---------- */
  .page-title {
    font-family: 'Noto Sans', sans-serif;
    font-weight: 800;
    font-size: clamp(26px, 6vw, 32px);
    text-align: center;
  }

  .page-sub {
    font-size: 14px;
    color: var(--text-soft);
    text-align: center;
    line-height: 1.5;
    margin-top: -8px;
  }

  /* ---------- version cards ---------- */
  .version-card {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: 24px;
    padding: 20px 20px;
    display: flex;
    flex-direction: column;
    gap: 14px;
  }

  .version-card.current {
    border-color: var(--circle);
  }

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

  .version-num {
    font-family: 'Noto Sans', sans-serif;
    font-weight: 800;
    font-size: 17px;
  }

  .version-badge {
    font-size: 11px;
    font-weight: 700;
    color: #fff;
    background: var(--circle);
    padding: 3px 10px;
    border-radius: 10px;
  }

  .changes {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    flex-direction: column;
    gap: 10px;
  }

  .changes li {
    position: relative;
    padding-left: 18px;
    font-size: 14px;
    line-height: 1.5;
    color: var(--text);
  }

  .changes li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 8px;
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--circle);
  }

  .changes b { font-weight: 700; }

  .changes code {
    font-family: monospace;
    font-size: 12.5px;
    background: var(--toggle-bg);
    padding: 1px 6px;
    border-radius: 6px;
    border: 1px solid var(--card-border);
  }