:root {
    --bg: #0f0f0f;
    --surface: #1a1a1a;
    --card: #222222;
    --border: #2e2e2e;
    --accent: #c8a96e;
    --accent-dim: #8a6f3f;
    --flag-red: #CF142B;
    --flag-blue: #00247D;
    --text: #e8e4dc;
    --text-muted: #7a7570;
    --text-secondary: #a09890;
    --green: #4caf7d;
    --green-dim: #1e3d2b;
    --radius: 10px;
    --font-main: 'Georgia', serif;
    --font-ui: 'Helvetica Neue', Arial, sans-serif;
  }

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

  body {
    background: var(--bg);
    color: var(--text);
    font-family: var(--font-ui);
    min-height: 100vh;
  }

  /* HEADER */
  .site-header {
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    padding: 1.25rem 2rem;
    display: flex;
    align-items: center;
    gap: 1rem;
    position: sticky;
    top: 0;
    z-index: 100;
  }

  .flag {
    display: flex;
    align-items: center;
    gap: 6px;
  }

  .flag-icon {
    width: 28px;
    height: 19px;
    border-radius: 3px;
    overflow: hidden;
    flex-shrink: 0;
  }

  .site-title {
    font-size: 1.1rem;
    font-weight: 600;
    letter-spacing: 0.02em;
    color: var(--text);
  }

  .site-subtitle {
    font-size: 0.78rem;
    color: var(--text-muted);
    letter-spacing: 0.08em;
    text-transform: uppercase;
  }

  .header-right {
    margin-left: auto;
    display: flex;
    align-items: center;
    gap: 12px;
  }

  .lesson-badge {
    background: var(--accent-dim);
    color: var(--accent);
    font-size: 0.72rem;
    font-weight: 600;
    padding: 4px 10px;
    border-radius: 20px;
    letter-spacing: 0.06em;
    text-transform: uppercase;
  }

  .level-badge {
    background: #1a2e1e;
    color: var(--green);
    font-size: 0.72rem;
    font-weight: 600;
    padding: 4px 10px;
    border-radius: 20px;
    letter-spacing: 0.06em;
  }

  /* HERO */
  .hero {
    background: linear-gradient(160deg, #141414 0%, #1a1510 100%);
    border-bottom: 1px solid var(--border);
    padding: 3rem 2rem 2.5rem;
    text-align: center;
  }

  .hero-eyebrow {
    font-size: 0.75rem;
    letter-spacing: 0.14em;
    text-transform: uppercase;
    color: var(--accent);
    margin-bottom: 0.75rem;
  }

  .hero-title {
    font-family: var(--font-main);
    font-size: 2.4rem;
    font-weight: normal;
    color: var(--text);
    margin-bottom: 0.6rem;
    line-height: 1.2;
  }

  .hero-desc {
    font-size: 0.92rem;
    color: var(--text-secondary);
    max-width: 520px;
    margin: 0 auto 1.5rem;
    line-height: 1.6;
  }

  .pareto-banner {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    background: var(--card);
    border: 1px solid var(--border);
    border-left: 3px solid var(--accent);
    padding: 0.6rem 1rem;
    border-radius: var(--radius);
    font-size: 0.82rem;
    color: var(--text-secondary);
  }

  .pareto-banner strong { color: var(--accent); }

  /* PROGRESS */
  .progress-section {
    padding: 1.5rem 2rem;
    max-width: 900px;
    margin: 0 auto;
  }

  .progress-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 12px;
  }

  .progress-card {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1rem 1.2rem;
  }

  .progress-label {
    font-size: 0.72rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-muted);
    margin-bottom: 6px;
  }

  .progress-value {
    font-size: 1.6rem;
    font-weight: 600;
    color: var(--text);
  }

  .progress-value span {
    font-size: 0.82rem;
    color: var(--text-muted);
    font-weight: 400;
  }

  .progress-bar-wrap {
    margin-top: 8px;
    background: var(--border);
    height: 3px;
    border-radius: 2px;
    overflow: hidden;
  }

  .progress-bar-fill {
    height: 100%;
    background: var(--accent);
    border-radius: 2px;
    transition: width 0.8s ease;
  }

  /* MAIN CONTENT */
  .main {
    max-width: 900px;
    margin: 0 auto;
    padding: 0 2rem 4rem;
  }

  .section-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin: 2.5rem 0 1rem;
    padding-bottom: 0.75rem;
    border-bottom: 1px solid var(--border);
  }

  .section-number {
    background: var(--accent);
    color: #0f0f0f;
    width: 26px;
    height: 26px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.78rem;
    font-weight: 700;
    flex-shrink: 0;
  }

  .section-title {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text);
    letter-spacing: 0.02em;
  }

  .section-count {
    margin-left: auto;
    font-size: 0.75rem;
    color: var(--text-muted);
  }

  /* PHRASE CARDS */
  .phrase-grid {
    display: grid;
    gap: 10px;
  }

  .phrase-card {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.1rem 1.3rem;
    display: grid;
    grid-template-columns: 1fr 1fr 1fr auto;
    gap: 1rem;
    align-items: center;
    transition: border-color 0.2s, background 0.2s;
    cursor: default;
  }

  .phrase-card:hover {
    border-color: var(--accent-dim);
    background: #272218;
  }

  .phrase-card.mastered {
    border-color: #2a4a35;
    background: #141e18;
  }

  .phrase-col-label {
    font-size: 0.65rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--text-muted);
    margin-bottom: 3px;
  }

  .phrase-english {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text);
    font-family: var(--font-main);
    font-style: italic;
  }

  .phrase-phonetic {
    font-size: 0.9rem;
    color: var(--accent);
    font-family: 'Courier New', monospace;
    letter-spacing: 0.04em;
  }

  .phrase-spanish {
    font-size: 0.9rem;
    color: var(--text-secondary);
  }

  .btn-master {
    background: transparent;
    border: 1px solid var(--border);
    color: var(--text-muted);
    width: 32px;
    height: 32px;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.9rem;
    transition: all 0.2s;
    flex-shrink: 0;
  }

  .btn-master:hover {
    border-color: var(--green);
    color: var(--green);
    background: var(--green-dim);
  }

  .phrase-card.mastered .btn-master {
    border-color: var(--green);
    color: var(--green);
    background: var(--green-dim);
  }

  /* PRONUNCIATION GUIDE */
  .pronun-box {
    background: var(--card);
    border: 1px solid var(--border);
    border-left: 3px solid var(--accent);
    border-radius: var(--radius);
    padding: 1.2rem 1.4rem;
    margin-bottom: 1rem;
  }

  .pronun-title {
    font-size: 0.78rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--accent);
    margin-bottom: 0.75rem;
  }

  .pronun-rules {
    display: grid;
    gap: 8px;
  }

  .pronun-rule {
    display: flex;
    align-items: flex-start;
    gap: 10px;
    font-size: 0.85rem;
    line-height: 1.5;
    color: var(--text-secondary);
  }

  .pronun-rule code {
    background: #2a2520;
    color: var(--accent);
    padding: 1px 6px;
    border-radius: 4px;
    font-size: 0.8rem;
    white-space: nowrap;
    flex-shrink: 0;
  }

  /* QUIZ SECTION */
  .quiz-wrap {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.5rem;
  }

  .quiz-question {
    font-size: 1rem;
    color: var(--text);
    margin-bottom: 1rem;
    font-family: var(--font-main);
    font-style: italic;
  }

  .quiz-options {
    display: grid;
    gap: 8px;
    margin-bottom: 1rem;
  }

  .quiz-option {
    background: #1e1e1e;
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 0.7rem 1rem;
    font-size: 0.88rem;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all 0.15s;
    text-align: left;
    font-family: 'Courier New', monospace;
  }

  .quiz-option:hover { border-color: var(--accent-dim); color: var(--text); }
  .quiz-option.correct { border-color: var(--green); background: var(--green-dim); color: var(--green); }
  .quiz-option.wrong { border-color: #7a2020; background: #2a1515; color: #e06060; }

  .quiz-feedback {
    font-size: 0.85rem;
    padding: 0.6rem 0;
    min-height: 1.5rem;
    color: var(--text-muted);
  }

  .quiz-nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-top: 1rem;
  }

  .quiz-counter {
    font-size: 0.78rem;
    color: var(--text-muted);
  }

  .btn-next {
    background: var(--accent);
    color: #0f0f0f;
    border: none;
    padding: 0.5rem 1.2rem;
    border-radius: 6px;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    transition: opacity 0.2s;
  }

  .btn-next:hover { opacity: 0.85; }
  .btn-next:disabled { opacity: 0.3; cursor: default; }

  /* FOOTER NAV */
  .lesson-nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 3rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border);
  }

  .btn-lesson {
    background: var(--card);
    border: 1px solid var(--border);
    color: var(--text-secondary);
    padding: 0.6rem 1.2rem;
    border-radius: 8px;
    font-size: 0.85rem;
    cursor: pointer;
    transition: all 0.2s;
  }

  .btn-lesson:hover { border-color: var(--accent-dim); color: var(--text); }
  .btn-lesson.primary { background: var(--accent); border-color: var(--accent); color: #0f0f0f; font-weight: 600; }
  .btn-lesson.primary:hover { opacity: 0.85; }

  .lesson-info {
    font-size: 0.78rem;
    color: var(--text-muted);
    text-align: center;
  }

  /* PHONETIC KEY */
  .phonetic-key {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
    gap: 8px;
  }

  .phonetic-item {
    background: #1a1a1a;
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 0.65rem 0.9rem;
    display: flex;
    gap: 8px;
    align-items: center;
  }

  .ph-symbol {
    font-family: 'Courier New', monospace;
    font-size: 0.95rem;
    color: var(--accent);
    min-width: 40px;
  }

  .ph-example {
    font-size: 0.78rem;
    color: var(--text-secondary);
    line-height: 1.4;
  }

  .ph-example em { color: var(--text-muted); font-style: normal; font-size: 0.72rem; }

  @media (max-width: 680px) {
    .phrase-card { grid-template-columns: 1fr 1fr; grid-template-rows: auto auto; }
    .phrase-card > *:last-child { grid-column: span 2; justify-self: end; }
    .progress-grid { grid-template-columns: 1fr; }
    .hero-title { font-size: 1.8rem; }
    .main, .progress-section { padding-left: 1rem; padding-right: 1rem; }
    .site-header { padding: 1rem; }
  }