/* ═══════════════════════════════════════════════════════════
     DESIGN REFRESH — дополнительные переменные и стили поверх styles.css
     ═══════════════════════════════════════════════════════════ */
  :root {
    --py-orange:  #ff6b35;
    --py-yellow:  #ffd166;
    --py-blue:    #1cb0f6;
    --py-teal:    #06d6a0;
    --py-purple:  #9b5de5;
    --py-pink:    #f72585;

    --glow-blue:  rgba(28,176,246,.18);
    --glow-green: rgba(6,214,160,.15);
    --glow-oran:  rgba(255,107,53,.15);

    --r4: 24px;
    --transition: all .2s cubic-bezier(.16,1,.3,1);
  }

  /* ── Сайдбар — обновлённый стиль ── */
  .sidebar-logo { padding: 8px 12px; }
  .logo-mark {
    font-size: 20px; font-weight: 900;
    background: linear-gradient(135deg, var(--py-blue), var(--py-teal));
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
    background-clip: text;
  }
  .nav-item {
    position: relative;
    letter-spacing: .01em;
  }
  .nav-item::before {
    content: ''; position: absolute; left: 0; top: 50%;
    transform: translateY(-50%); height: 60%; width: 3px;
    background: var(--py-blue); border-radius: 0 2px 2px 0;
    opacity: 0; transition: opacity .2s;
  }
  .nav-item.active::before { opacity: 1; }

  /* ── Прелоадер обновлённый ── */
  .preloader-logo {
    background: linear-gradient(135deg, var(--py-blue), var(--py-teal));
    -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text;
  }

  /* ═══════════════════════════════════════
     ИНТЕРАКТИВНЫЕ УРОКИ — новый дизайн
     ═══════════════════════════════════════ */

  /* Хедер секции */
  .sl-hero {
    background: linear-gradient(135deg, var(--bg2) 0%, var(--bg3) 100%);
    border-bottom: 1px solid var(--border);
    padding: 32px 28px 0;
    position: relative;
    overflow: hidden;
  }
  .sl-hero::before {
    content: '';
    position: absolute; inset: 0;
    background: radial-gradient(ellipse at 80% 50%, var(--glow-blue) 0%, transparent 65%),
                radial-gradient(ellipse at 10% 100%, var(--glow-green) 0%, transparent 55%);
    pointer-events: none;
  }
  .sl-hero-grid {
    display: grid;
    grid-template-columns: 1fr auto;
    align-items: flex-start;
    gap: 24px;
    position: relative;
    z-index: 1;
  }
  .sl-hero-eyebrow {
    font-family: var(--mono); font-size: 10px; font-weight: 700;
    color: var(--py-teal); letter-spacing: .2em; text-transform: uppercase;
    margin-bottom: 8px;
  }
  .sl-hero-title {
    font-size: 28px; font-weight: 900;
    background: linear-gradient(135deg, #fff 30%, var(--py-blue));
    -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text;
    line-height: 1.15; margin-bottom: 8px; letter-spacing: -.5px;
  }
  .sl-hero-sub {
    font-size: 13px; color: var(--text3); max-width: 480px; line-height: 1.6;
  }
  .sl-hero-actions {
    display: flex; flex-direction: column; gap: 10px; align-items: flex-end; flex-shrink: 0;
  }
  .sl-btn-primary {
    background: linear-gradient(135deg, var(--py-blue), var(--py-teal));
    color: #fff; border: none;
    padding: 11px 22px; border-radius: var(--r3);
    font-family: var(--font); font-size: 13px; font-weight: 800;
    cursor: pointer; transition: var(--transition);
    box-shadow: 0 4px 16px rgba(28,176,246,.35);
    white-space: nowrap;
  }
  .sl-btn-primary:hover { filter: brightness(1.1); transform: translateY(-2px); }
  .sl-btn-secondary {
    background: transparent; color: var(--text2);
    border: 2px solid var(--border2);
    padding: 9px 20px; border-radius: var(--r3);
    font-family: var(--font); font-size: 13px; font-weight: 700;
    cursor: pointer; transition: var(--transition); white-space: nowrap;
  }
  .sl-btn-secondary:hover { border-color: var(--border3); color: var(--text); }

  /* Статистика под хедером */
  .sl-stats {
    display: flex; gap: 0; margin-top: 24px;
    border-top: 1px solid var(--border);
    position: relative; z-index: 1;
  }
  .sl-stat {
    flex: 1; padding: 16px 20px;
    border-right: 1px solid var(--border);
    display: flex; flex-direction: column; gap: 3px;
    transition: background .15s;
  }
  .sl-stat:last-child { border-right: none; }
  .sl-stat:hover { background: rgba(255,255,255,.03); }
  .sl-stat-num {
    font-size: 22px; font-weight: 900; color: var(--py-blue);
    font-family: var(--mono); line-height: 1;
  }
  .sl-stat-lbl {
    font-family: var(--mono); font-size: 9px; color: var(--text3);
    text-transform: uppercase; letter-spacing: .12em;
  }

  /* Таб-бар */
  .sl-tabs {
    display: flex; align-items: center; gap: 0;
    border-bottom: 1px solid var(--border);
    background: var(--bg-blur); backdrop-filter: blur(20px);
    position: sticky; top: 0; z-index: 10;
    overflow-x: auto; scrollbar-width: none;
  }
  .sl-tabs::-webkit-scrollbar { display: none; }
  .sl-tab {
    flex-shrink: 0; display: flex; align-items: center; gap: 7px;
    padding: 14px 18px;
    background: transparent; border: none;
    border-bottom: 3px solid transparent;
    color: var(--text3); font-family: var(--font);
    font-size: 12px; font-weight: 800; cursor: pointer;
    transition: all .15s; letter-spacing: .05em;
    text-transform: uppercase; margin-bottom: -1px;
  }
  .sl-tab svg { width: 14px; height: 14px; opacity: .6; }
  .sl-tab:hover { color: var(--text2); }
  .sl-tab.active {
    color: var(--py-blue); border-bottom-color: var(--py-blue);
  }
  .sl-tab.active svg { opacity: 1; }
  .sl-tab-badge {
    font-family: var(--mono); font-size: 9px; font-weight: 800;
    background: rgba(28,176,246,.15); color: var(--py-blue);
    padding: 2px 7px; border-radius: 99px; min-width: 20px; text-align: center;
  }

  /* Панели */
  .sl-panel { display: none; }
  .sl-panel.active {
    display: block;
    animation: fadeUpSmooth .35s cubic-bezier(.16,1,.3,1) both;
  }

  /* ═══════════════════════════════════════
     АДАПТАЦИЯ — sl-hero / sl-stats / sl-tabs
     (бұл блоктарда мобильді бейімдеу мүлдем болмаған)
     ═══════════════════════════════════════ */
  @media (max-width: 900px) {
    .sl-hero { padding: 22px 18px 0; }
    .sl-hero-grid {
      grid-template-columns: 1fr;
      gap: 18px;
    }
    .sl-hero-title { font-size: 22px; }
    .sl-hero-sub { max-width: none; }
    .sl-hero-actions {
      flex-direction: row;
      align-items: stretch;
      width: 100%;
      flex-wrap: wrap;
    }
    .sl-btn-primary, .sl-btn-secondary {
      flex: 1 1 auto;
      min-width: 140px;
      text-align: center;
      justify-content: center;
    }
    .sl-stats {
      flex-wrap: wrap;
      margin-top: 18px;
    }
    .sl-stat {
      flex: 1 1 50%;
      min-width: 0;
      border-right: 1px solid var(--border);
      border-bottom: 1px solid var(--border);
      padding: 12px 14px;
    }
    .sl-stat:nth-child(2n) { border-right: none; }
    .sl-stat:last-child, .sl-stat:nth-last-child(2):nth-child(odd) { border-bottom: none; }
    .sl-stat-num { font-size: 18px; }

    .sl-tabs { padding: 0 4px; }
    .sl-tab { padding: 12px 14px; font-size: 11px; }
  }
  @media (max-width: 480px) {
    .sl-hero-title { font-size: 19px; }
    .sl-hero-actions { flex-direction: column; }
    .sl-btn-primary, .sl-btn-secondary { width: 100%; }
    .sl-stat { flex: 1 1 100%; border-right: none; }
    .sl-tab { padding: 11px 12px; font-size: 10px; gap: 5px; }
    .sl-tab svg { width: 12px; height: 12px; }
  }

  /* ═══════════════════════════════════════════════════════════
     LANDING SCREEN — показывается незалогиненным пользователям
     ═══════════════════════════════════════════════════════════ */

  #landing-screen {
    position: fixed; inset: 0; z-index: 9998;
    background: var(--bg);
    display: flex; flex-direction: column;
    overflow-y: auto;
    transition: opacity .4s, visibility .4s;
  }
  #landing-screen.hidden { opacity: 0; visibility: hidden; pointer-events: none; display: none; }

  /* ── Навбар ── */
  .land-nav {
    display: flex; align-items: center; justify-content: space-between;
    padding: 20px 48px;
    border-bottom: 1px solid var(--border);
    position: sticky; top: 0;
    background: rgba(19,31,36,.94); backdrop-filter: blur(20px);
    z-index: 10;
  }
  .land-nav-logo { text-decoration: none; display: flex; flex-direction: column; gap: 2px; }
  .land-nav-logo .lnl-name { font-size: 20px; font-weight: 900; color: var(--duo-blue); letter-spacing: -1px; line-height: 1; }
  .land-nav-logo .lnl-sub  { font-family: var(--mono); font-size: 9px; color: var(--text3); letter-spacing: .15em; text-transform: uppercase; }
  .land-nav-btns { display: flex; gap: 10px; align-items: center; }
  .land-btn-ghost {
    padding: 9px 20px; border-radius: 99px;
    border: 1.5px solid var(--border2); background: transparent;
    color: var(--text2); font-family: var(--font); font-size: 13px; font-weight: 800;
    cursor: pointer; text-decoration: none; transition: all .15s;
  }
  .land-btn-ghost:hover { border-color: var(--duo-blue); color: var(--duo-blue); }
  .land-btn-solid {
    padding: 9px 20px; border-radius: 99px;
    background: var(--duo-blue); border: none;
    color: #fff; font-family: var(--font); font-size: 13px; font-weight: 900;
    cursor: pointer; text-decoration: none; transition: background .15s;
  }
  .land-btn-solid:hover { background: var(--duo-blue2); }

  /* ── Hero ── */
  .land-hero {
    display: flex; align-items: center; gap: 80px;
    padding: 80px 48px 64px;
    max-width: 1200px; margin: 0 auto; width: 100%;
  }
  .land-hero-left { flex: 1; }
  .land-hero-eyebrow {
    display: inline-flex; align-items: center; gap: 8px;
    background: rgba(28,176,246,.1); border: 1px solid rgba(28,176,246,.2);
    border-radius: 99px; padding: 5px 14px;
    font-family: var(--mono); font-size: 11px; color: var(--duo-blue);
    letter-spacing: .1em; text-transform: uppercase; margin-bottom: 24px;
  }
  .land-hero-eyebrow::before { content: '●'; font-size: 8px; color: var(--duo-teal); animation: pulse-dot 1.5s ease infinite; }
  @keyframes pulse-dot { 0%,100%{opacity:1} 50%{opacity:.3} }

  .land-hero-title {
    font-size: 56px; font-weight: 900; line-height: 1.1;
    color: var(--text); letter-spacing: -2px; margin-bottom: 20px;
  }
  .land-hero-title .ht-accent { color: var(--duo-blue); }
  .land-hero-title .ht-kz    { color: var(--duo-teal); font-size: 44px; display: block; margin-top: 4px; }

  .land-hero-sub {
    font-size: 17px; color: var(--text3); line-height: 1.65;
    max-width: 480px; margin-bottom: 36px;
  }

  .land-hero-cta { display: flex; gap: 12px; align-items: center; margin-bottom: 40px; flex-wrap: wrap; }
  .land-cta-main {
    padding: 15px 32px; border-radius: 99px;
    background: var(--duo-blue); border: none;
    color: #fff; font-family: var(--font); font-size: 16px; font-weight: 900;
    cursor: pointer; text-decoration: none; transition: background .15s;
    letter-spacing: .02em;
  }
  .land-cta-main:hover { background: var(--duo-blue2); }
  .land-cta-secondary {
    padding: 15px 28px; border-radius: 99px;
    border: 1.5px solid var(--border2); background: transparent;
    color: var(--text2); font-family: var(--font); font-size: 15px; font-weight: 800;
    cursor: pointer; text-decoration: none; transition: all .15s;
  }
  .land-cta-secondary:hover { border-color: var(--duo-blue); color: var(--duo-blue); }

  .land-hero-stats { display: flex; gap: 28px; flex-wrap: wrap; }
  .land-stat-item { display: flex; flex-direction: column; gap: 2px; }
  .land-stat-val { font-size: 22px; font-weight: 900; color: var(--text); line-height: 1; }
  .land-stat-lbl { font-size: 12px; color: var(--text3); font-weight: 600; }

  /* ── Hero визуалка ── */
  .land-hero-right { flex-shrink: 0; width: 380px; }
  .land-mockup {
    background: var(--bg2); border: 1px solid var(--border2);
    border-radius: 20px; padding: 20px; position: relative; overflow: hidden;
  }
  .land-mockup::before {
    content: ''; position: absolute; inset: 0; pointer-events: none;
    background: linear-gradient(135deg, rgba(28,176,246,.04) 0%, transparent 50%);
  }
  .lm-header { display: flex; align-items: center; gap: 10px; margin-bottom: 16px; }
  .lm-avatar { width: 32px; height: 32px; border-radius: 50%; background: var(--duo-blue); display: flex; align-items: center; justify-content: center; font-size: 14px; font-weight: 900; color: #fff; }
  .lm-title-block { flex: 1; }
  .lm-title-block strong { font-size: 13px; font-weight: 800; color: var(--text); display: block; }
  .lm-title-block span  { font-size: 11px; color: var(--text3); }
  .lm-live { background: rgba(255,75,75,.15); border: 1px solid rgba(255,75,75,.3); border-radius: 99px; padding: 3px 10px; font-family: var(--mono); font-size: 10px; color: var(--duo-red); font-weight: 700; letter-spacing: .05em; }
  .lm-slide {
    background: var(--bg3); border-radius: 12px; padding: 16px;
    margin-bottom: 12px; border: 1px solid var(--border);
  }
  .lm-slide-label { font-family: var(--mono); font-size: 10px; color: var(--text3); letter-spacing: .1em; text-transform: uppercase; margin-bottom: 10px; }
  .lm-code { font-family: var(--mono); font-size: 13px; color: var(--duo-teal); line-height: 1.6; }
  .lm-code .kw  { color: var(--duo-purple); }
  .lm-code .fn  { color: var(--duo-blue); }
  .lm-code .str { color: var(--duo-orange); }
  .lm-code .num { color: var(--duo-green); }
  .lm-quiz { background: var(--bg3); border-radius: 12px; padding: 14px; border: 1px solid var(--border); }
  .lm-quiz-q { font-size: 13px; font-weight: 800; color: var(--text2); margin-bottom: 10px; }
  .lm-opts { display: flex; flex-direction: column; gap: 6px; }
  .lm-opt {
    padding: 9px 12px; border-radius: 8px; border: 1.5px solid var(--border2);
    font-size: 12px; font-weight: 700; color: var(--text3); cursor: default;
  }
  .lm-opt.correct { border-color: var(--duo-green); color: var(--duo-green); background: rgba(87,204,2,.08); }
  .lm-opt.wrong   { border-color: var(--duo-red);   color: var(--duo-red);   background: rgba(255,75,75,.08); }
  .lm-viewers { display: flex; align-items: center; gap: 8px; margin-top: 12px; }
  .lm-avatars { display: flex; }
  .lm-mini-av { width: 22px; height: 22px; border-radius: 50%; border: 2px solid var(--bg2); margin-right: -6px; font-size: 10px; display: flex; align-items: center; justify-content: center; font-weight: 800; }
  .lm-viewers-txt { font-size: 11px; color: var(--text3); margin-left: 10px; }

  /* ── Секция фич ── */
  .land-features {
    padding: 64px 48px;
    max-width: 1200px; margin: 0 auto; width: 100%;
    border-top: 1px solid var(--border);
  }
  .land-feat-eyebrow {
    font-family: var(--mono); font-size: 11px; color: var(--text3);
    letter-spacing: .15em; text-transform: uppercase; margin-bottom: 12px;
  }
  .land-feat-title {
    font-size: 32px; font-weight: 900; color: var(--text);
    letter-spacing: -.5px; margin-bottom: 48px;
  }
  .land-feat-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
  .land-feat-card {
    background: var(--bg2); border: 1px solid var(--border2);
    border-radius: 16px; padding: 24px;
    transition: border-color .2s;
  }
  .land-feat-card:hover { border-color: var(--border3); }
  .lfc-icon {
    width: 44px; height: 44px; border-radius: 12px;
    display: flex; align-items: center; justify-content: center;
    font-size: 22px; margin-bottom: 16px; border: 1px solid var(--border2);
  }
  .lfc-blue   { background: rgba(28,176,246,.1);  border-color: rgba(28,176,246,.2); }
  .lfc-green  { background: rgba(87,204,2,.1);    border-color: rgba(87,204,2,.2); }
  .lfc-orange { background: rgba(255,150,0,.1);   border-color: rgba(255,150,0,.2); }
  .lfc-purple { background: rgba(206,130,255,.1); border-color: rgba(206,130,255,.2); }
  .lfc-teal   { background: rgba(31,224,192,.1);  border-color: rgba(31,224,192,.2); }
  .lfc-red    { background: rgba(255,75,75,.1);   border-color: rgba(255,75,75,.2); }
  .lfc-name { font-size: 15px; font-weight: 900; color: var(--text); margin-bottom: 6px; }
  .lfc-desc { font-size: 13px; color: var(--text3); line-height: 1.55; }

  /* ── Секция ролей ── */
  .land-roles {
    padding: 64px 48px;
    max-width: 1200px; margin: 0 auto; width: 100%;
    border-top: 1px solid var(--border);
  }
  .land-roles-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; margin-top: 48px; }
  .land-role-card {
    background: var(--bg2); border-radius: 20px; padding: 32px;
    border: 1px solid var(--border2); position: relative; overflow: hidden;
  }
  .land-role-card::before {
    content: ''; position: absolute; width: 300px; height: 300px; border-radius: 50%;
    top: -100px; right: -100px; pointer-events: none;
  }
  .lrc-student::before { background: radial-gradient(circle, rgba(28,176,246,.06) 0%, transparent 70%); }
  .lrc-teacher::before { background: radial-gradient(circle, rgba(255,150,0,.06) 0%, transparent 70%); }
  .lrc-badge {
    display: inline-flex; align-items: center; gap: 6px;
    border-radius: 99px; padding: 5px 12px; margin-bottom: 20px;
    font-size: 12px; font-weight: 800; letter-spacing: .04em;
  }
  .lrc-s-badge { background: rgba(28,176,246,.12); color: var(--duo-blue); border: 1px solid rgba(28,176,246,.2); }
  .lrc-t-badge { background: rgba(255,150,0,.12); color: var(--duo-orange); border: 1px solid rgba(255,150,0,.2); }
  .lrc-title { font-size: 24px; font-weight: 900; color: var(--text); margin-bottom: 10px; letter-spacing: -.3px; }
  .lrc-sub   { font-size: 14px; color: var(--text3); line-height: 1.6; margin-bottom: 24px; }
  .lrc-list  { list-style: none; display: flex; flex-direction: column; gap: 8px; margin-bottom: 28px; }
  .lrc-list li { font-size: 13px; color: var(--text2); display: flex; align-items: center; gap: 8px; }
  .lrc-list li::before { content: '✓'; color: var(--duo-green); font-weight: 900; font-size: 14px; }
  .lrc-cta {
    display: inline-block; padding: 12px 24px; border-radius: 99px;
    font-family: var(--font); font-size: 14px; font-weight: 900;
    cursor: pointer; text-decoration: none; transition: all .15s; border: none;
  }
  .lrc-s-cta { background: var(--duo-blue); color: #fff; }
  .lrc-s-cta:hover { background: var(--duo-blue2); }
  .lrc-t-cta { background: rgba(255,150,0,.15); color: var(--duo-orange); border: 1.5px solid rgba(255,150,0,.3); }
  .lrc-t-cta:hover { background: rgba(255,150,0,.25); }

  /* ── Footer ── */
  .land-footer {
    border-top: 1px solid var(--border);
    padding: 28px 48px;
    display: flex; align-items: center; justify-content: space-between;
  }
  .land-footer-logo { font-family: var(--mono); font-size: 12px; color: var(--text3); }
  .land-footer-right { font-family: var(--mono); font-size: 11px; color: var(--text3); }

  /* Mobile */
  @media (max-width: 900px) {
    .land-nav { padding: 14px 18px; }
    .land-nav-btns { gap: 6px; flex-wrap: wrap; justify-content: flex-end; }
    .land-btn-ghost, .land-btn-solid { padding: 8px 16px; font-size: 12px; }
    .land-hero { flex-direction: column; padding: 36px 18px; gap: 32px; }
    .land-hero-title { font-size: 32px; }
    .land-hero-right { width: 100%; }
    .land-hero-cta { flex-direction: column; align-items: stretch; }
    .land-cta-main, .land-cta-secondary { text-align: center; width: 100%; box-sizing: border-box; }
    .land-hero-stats { gap: 16px; }
    .land-features, .land-roles { padding: 36px 18px; }
    .land-feat-title { font-size: 24px; }
    .land-feat-grid { grid-template-columns: 1fr 1fr; gap: 10px; }
    .land-feat-card { padding: 16px; }
    .land-roles-grid { grid-template-columns: 1fr; }
    .land-role-card { padding: 20px; }
    .lrc-title { font-size: 19px; }
    .land-footer { padding: 18px; flex-direction: column; gap: 8px; text-align: center; }
    .lm-header { gap: 8px; }
  }
  @media (max-width: 560px) {
    .land-feat-grid { grid-template-columns: 1fr; }
    .land-hero-stats { gap: 14px; }
    .land-hero-title { font-size: 25px; }
    .land-hero-title .ht-kz { font-size: 19px; }
    .land-hero-sub { font-size: 14px; }
    .land-mockup { padding: 14px; }
  }