:root {
    --bg: #0a0e1a;
    --surface: #111827;
    --surface2: #1a2236;
    --border: rgba(99,179,237,0.15);
    --accent1: #63b3ed;
    --accent2: #9f7aea;
    --correct: #48bb78;
    --correct-bg: rgba(72,187,120,0.12);
    --correct-border: rgba(72,187,120,0.5);
    --wrong: #fc8181;
    --wrong-bg: rgba(252,129,129,0.1);
    --wrong-border: rgba(252,129,129,0.5);
    --text: #e2e8f0;
    --muted: #8896a8;
    --highlight: rgba(99,179,237,0.12);
    --grad1: linear-gradient(135deg, #63b3ed 0%, #9f7aea 100%);
    --grad2: linear-gradient(135deg, #0a0e1a 0%, #1a1a2e 50%, #0d1b2a 100%);
  }
  *, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

  body {
    font-family: 'Sora', sans-serif;
    background: #0e4a2a url('../assets/textcompletion-bg.jpg') no-repeat center center fixed;
    background-size: cover;
    min-height: 100vh;
    color: var(--text);
    overflow-x: hidden;
  }

  body::before, body::after {
    content: '';
    position: fixed;
    border-radius: 50%;
    filter: blur(120px);
    pointer-events: none;
    z-index: 0;
  }
  body::before {
    width: 600px; height: 600px;
    background: radial-gradient(circle, rgba(99,179,237,0.08) 0%, transparent 70%);
    top: -200px; left: -200px;
  }
  body::after {
    width: 500px; height: 500px;
    background: radial-gradient(circle, rgba(159,122,234,0.07) 0%, transparent 70%);
    bottom: -150px; right: -150px;
  }

  .container {
    max-width: 1440px;
    width: 96vw;
    margin: 0 auto;
    padding: 2rem 1.25rem 3.5rem;
    position: relative;
    z-index: 1;
  }

  .exam-layout {
    display: grid;
    grid-template-columns: minmax(0, 1.15fr) minmax(0, 1fr);
    gap: 2.25rem;
    align-items: start;
  }

  @media (max-width: 900px) {
    .exam-layout {
      grid-template-columns: 1fr;
    }
  }

  .left-col {
    position: sticky;
    top: 2rem;
    max-height: calc(100vh - 4rem);
    overflow-y: auto;
    /* Custom scrollbar for the passage area */
    scrollbar-width: thin;
    scrollbar-color: var(--accent1) var(--surface);
  }
  .left-col::-webkit-scrollbar {
    width: 6px;
  }
  .left-col::-webkit-scrollbar-track {
    background: var(--surface);
    border-radius: 4px;
  }
  .left-col::-webkit-scrollbar-thumb {
    background-color: var(--accent1);
    border-radius: 4px;
  }

  .right-col {
    display: flex;
    flex-direction: column;
  }

  .exam-header {
    text-align: center;
    margin-bottom: 2.5rem;
    animation: fadeDown 0.7s ease both;
    position: relative;
  }
  .home-btn {
    position: absolute;
    left: 0;
    top: 0;
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 8px 16px;
    border-radius: 10px;
    background: rgba(255,255,255,0.05);
    border: 1px solid var(--border);
    color: var(--text);
    text-decoration: none;
    font-size: 13px;
    font-weight: 500;
    transition: all 0.2s;
    z-index: 10;
  }
  .home-btn:hover {
    background: var(--highlight);
    border-color: var(--accent1);
    transform: translateY(-1px);
  }
  /* Nút Sổ câu sai: góc phải đầu trang, cùng kiểu nút Home */
  .review-btn {
    left: auto;
    right: 0;
  }
  .review-btn b { color: var(--wrong); }
  .result-review {
    justify-content: center;
    margin-top: 10px;
    width: 100%;
    text-decoration: none;
  }
  .result-review b { color: var(--wrong); }
  @media (max-width: 600px) {
    .home-btn {
      position: static;
      margin-bottom: 1.5rem;
      justify-content: center;
      width: fit-content;
      margin-left: auto;
      margin-right: auto;
    }
  }
  .badge {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    background: rgba(99,179,237,0.1);
    border: 1px solid rgba(99,179,237,0.3);
    border-radius: 100px;
    padding: 5px 16px;
    font-size: 11px;
    font-weight: 600;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    color: var(--accent1);
    margin-bottom: 1rem;
  }
  .badge-dot {
    width: 6px; height: 6px;
    border-radius: 50%;
    background: var(--accent1);
    animation: pulse 2s infinite;
  }
  h1 {
    font-size: clamp(1.6rem, 4vw, 2.4rem);
    font-weight: 700;
    background: var(--grad1);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    line-height: 1.2;
    margin-bottom: 0.5rem;
  }
  .subtitle {
    font-size: 0.85rem;
    color: var(--muted);
    font-weight: 300;
    letter-spacing: 0.02em;
  }

  .scorebar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 14px;
    padding: 0.9rem 1.25rem;
    margin-bottom: 1.75rem;
    animation: fadeDown 0.7s 0.1s ease both;
    gap: 1rem;
  }
  .score-item { text-align: center; flex-shrink: 0; }
  .score-item .val {
    font-size: 1.5rem;
    font-weight: 700;
    font-family: 'JetBrains Mono', monospace;
    background: var(--grad1);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
  }
  .score-item .lbl { font-size: 10px; color: var(--muted); text-transform: uppercase; letter-spacing: 0.08em; margin-top: 2px; }
  .progress-wrap { flex: 1; }
  .progress-track {
    background: rgba(255,255,255,0.06);
    border-radius: 100px;
    height: 6px;
    overflow: hidden;
  }
  .progress-fill {
    height: 100%;
    border-radius: 100px;
    background: var(--grad1);
    transition: width 0.5s cubic-bezier(0.4,0,0.2,1);
    width: 0%;
  }
  .progress-lbl { font-size: 11px; color: var(--muted); margin-top: 5px; text-align: right; }

  .section-title {
    font-size: 10px;
    font-weight: 600;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--accent1);
    margin-bottom: 0.75rem;
    display: flex;
    align-items: center;
    gap: 8px;
  }
  .section-title::after {
    content: '';
    flex: 1;
    height: 1px;
    background: var(--border);
  }

  .passage-card {
    background: rgba(17, 24, 39, 0.75);
    border: 1px solid var(--border);
    border-radius: 16px;
    padding: 2rem 2.25rem;
    margin-bottom: 2rem;
    font-size: 1.05rem;
    line-height: 2.1;
    color: #dbe4ee;
    animation: fadeUp 0.6s 0.2s ease both;
    position: relative;
    overflow: hidden;
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    box-shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.3);
  }
  .passage-card::before {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0;
    height: 3px;
    background: var(--grad1);
  }
  .passage-title {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text);
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 12px;
  }
  .passage-tag {
    font-size: 0.75rem;
    font-weight: 600;
    background: var(--highlight);
    color: var(--accent1);
    border: 1px solid rgba(99,179,237,0.25);
    border-radius: 6px;
    padding: 3px 10px;
  }
  .blank-tag {
    display: inline-block;
    font-family: 'JetBrains Mono', monospace;
    font-size: 13px;
    font-weight: 700;
    background: rgba(159,122,234,0.2);
    color: #ddd6fe;
    border: 1.5px solid rgba(159,122,234,0.45);
    border-radius: 6px;
    padding: 2px 9px;
    margin: 0 3px;
    vertical-align: baseline;
  }
  .passage-meta {
    display: flex;
    align-items: center;
    gap: 6px;
    font-size: 11px;
    color: var(--muted);
    margin-bottom: 1rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid var(--border);
    font-style: italic;
  }

  .instruction {
    font-size: 0.95rem;
    color: var(--muted);
    text-align: left;
    margin-bottom: 1.25rem;
    font-style: italic;
    line-height: 1.5;
  }

  .questions-wrap { display: flex; flex-direction: column; gap: 1.4rem; }

  .q-card {
    background: rgba(17, 24, 39, 0.75);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid var(--border);
    border-radius: 16px;
    overflow: hidden;
    animation: fadeUp 0.5s ease both;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: 0 4px 15px rgba(0,0,0,0.15);
  }
  .q-card:hover { 
    border-color: rgba(99,179,237,0.4);
    transform: translateY(-3px);
    box-shadow: 0 12px 25px rgba(0,0,0,0.3);
  }

  .q-header {
    display: flex;
    align-items: center;
    gap: 14px;
    padding: 1.1rem 1.4rem;
    border-bottom: 1px solid var(--border);
    background: rgba(255,255,255,0.02);
  }
  .q-num {
    width: 38px; height: 38px;
    border-radius: 10px;
    background: var(--grad1);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 14px;
    font-weight: 800;
    color: white;
    flex-shrink: 0;
    font-family: 'JetBrains Mono', monospace;
  }
  .q-title {
    font-size: 1.15rem;
    font-weight: 700;
    color: var(--text);
  }
  .q-type {
    font-size: 11px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--muted);
  }
  .q-body { padding: 1.4rem; }

  .options { display: flex; flex-direction: column; gap: 10px; }

  .opt {
    display: flex;
    align-items: center;
    gap: 14px;
    padding: 14px 18px;
    border-radius: 12px;
    border: 1px solid rgba(255,255,255,0.08);
    cursor: pointer;
    font-size: 1.05rem;
    color: var(--text);
    background: rgba(255,255,255,0.03);
    transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
    line-height: 1.55;
    position: relative;
    overflow: hidden;
  }
  .opt::before {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0; bottom: 0;
    background: linear-gradient(120deg, transparent, rgba(255,255,255,0.04), transparent);
    transform: translateX(-100%);
    transition: transform 0.6s;
    pointer-events: none;
  }
  .opt:hover:not(.locked) {
    border-color: rgba(99,179,237,0.45);
    background: rgba(99,179,237,0.12);
    transform: translateX(4px);
  }
  .opt:hover:not(.locked)::before {
    transform: translateX(100%);
  }
  .opt-letter {
    width: 28px; height: 28px;
    border-radius: 8px;
    background: rgba(255,255,255,0.06);
    border: 1px solid rgba(255,255,255,0.12);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 13px;
    font-weight: 700;
    font-family: 'JetBrains Mono', monospace;
    flex-shrink: 0;
    transition: all 0.2s;
    color: var(--muted);
  }
  .opt.correct {
    border-color: var(--correct-border);
    background: var(--correct-bg);
    color: #c6f6d5;
    font-weight: 600;
  }
  .opt.correct .opt-letter {
    background: var(--correct);
    border-color: var(--correct);
    color: white;
  }
  .opt.wrong {
    border-color: var(--wrong-border);
    background: var(--wrong-bg);
    color: #fed7d7;
  }
  .opt.wrong .opt-letter {
    background: var(--wrong);
    border-color: var(--wrong);
    color: white;
  }
  .opt.locked { cursor: default; pointer-events: none; }
  .opt.dimmed { opacity: 0.32; }

  .feedback {
    display: none;
    margin-top: 1.1rem;
    padding: 14px 18px;
    border-radius: 12px;
    font-size: 0.95rem;
    line-height: 1.65;
    animation: slideIn 0.3s ease;
  }
  .feedback.show { display: block; }
  .feedback.ok {
    background: var(--correct-bg);
    border: 1px solid var(--correct-border);
    color: #9ae6b4;
  }
  .feedback.err {
    background: var(--wrong-bg);
    border: 1px solid var(--wrong-border);
    color: #feb2b2;
  }
  .fb-row { display: flex; gap: 8px; margin-bottom: 4px; align-items: flex-start; }
  .fb-icon { font-size: 14px; flex-shrink: 0; margin-top: 1px; }
  .fb-title { font-weight: 600; font-size: 12px; text-transform: uppercase; letter-spacing: 0.05em; }
  .fb-explain { font-size: 12.5px; color: rgba(255,255,255,0.65); margin-top: 6px; border-top: 1px solid rgba(255,255,255,0.08); padding-top: 6px; }
  .fb-grammar {
    font-family: 'JetBrains Mono', monospace;
    font-size: 11px;
    color: #c4b5fd;
    background: rgba(159,122,234,0.1);
    border-radius: 4px;
    padding: 2px 6px;
  }

  .actions {
    display: flex;
    gap: 10px;
    margin-top: 2rem;
    flex-wrap: wrap;
    animation: fadeUp 0.5s 0.5s ease both;
  }
  .btn {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 10px 20px;
    border-radius: 10px;
    font-family: 'Sora', sans-serif;
    font-size: 13px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    border: none;
  }
  .btn-primary {
    background: var(--grad1);
    color: white;
  }
  .btn-primary:hover { opacity: 0.88; transform: translateY(-1px); }
  .btn-ghost {
    background: transparent;
    border: 1px solid rgba(255,255,255,0.15);
    color: var(--muted);
  }
  .btn-ghost:hover { border-color: rgba(255,255,255,0.3); color: var(--text); }

  .result-panel {
    display: none;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 16px;
    padding: 2rem;
    margin-top: 2rem;
    text-align: center;
    animation: fadeUp 0.5s ease;
    position: relative;
    overflow: hidden;
  }
  .result-panel::before {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0;
    height: 3px;
    background: var(--grad1);
  }
  .result-grade {
    font-size: 3.5rem;
    font-weight: 700;
    font-family: 'JetBrains Mono', monospace;
    background: var(--grad1);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    line-height: 1;
    margin-bottom: 0.5rem;
  }
  .result-msg { font-size: 0.9rem; color: var(--muted); margin-bottom: 1.25rem; }
  .result-stats {
    display: flex;
    justify-content: center;
    gap: 2rem;
    font-size: 13px;
    color: var(--muted);
  }
  .result-stats span { color: var(--text); font-weight: 500; }

  @keyframes fadeDown {
    from { opacity: 0; transform: translateY(-16px); }
    to { opacity: 1; transform: translateY(0); }
  }
  @keyframes fadeUp {
    from { opacity: 0; transform: translateY(16px); }
    to { opacity: 1; transform: translateY(0); }
  }
  @keyframes slideIn {
    from { opacity: 0; transform: translateY(6px); }
    to { opacity: 1; transform: translateY(0); }
  }
  @keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.4; }
  }

  .q-card:nth-child(1) { animation-delay: 0.1s; }
  .q-card:nth-child(2) { animation-delay: 0.15s; }
  .q-card:nth-child(3) { animation-delay: 0.2s; }
  .q-card:nth-child(4) { animation-delay: 0.25s; }
  .q-card:nth-child(5) { animation-delay: 0.3s; }

  .instruction {
    font-size: 12px;
    color: var(--muted);
    text-align: center;
    margin-bottom: 1.5rem;
    font-style: italic;
  }

  /* Selection Screen Styles */
  .select-screen {
    max-width: 800px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
  }
  .exam-option {
    background: rgba(17, 24, 39, 0.8);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border: 1px solid var(--border);
    border-radius: 16px;
    padding: 1.5rem 2rem;
    cursor: pointer;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: relative;
    overflow: hidden;
  }
  .exam-option::after {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0; bottom: 0;
    background: linear-gradient(120deg, transparent, rgba(99,179,237,0.06), transparent);
    transform: translateX(-100%);
    transition: transform 0.6s;
    pointer-events: none;
  }
  .exam-option:hover {
    border-color: var(--accent1);
    transform: translateY(-4px) scale(1.01);
    background: rgba(255,255,255,0.04);
    box-shadow: 0 12px 30px rgba(0,0,0,0.3);
  }
  .exam-option:hover::after {
    transform: translateX(100%);
  }
  .eo-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text);
    margin-bottom: 0.5rem;
  }
  .eo-meta {
    font-size: 0.85rem;
    color: var(--muted);
  }
  /* Tiến độ đã lưu của từng đề trên màn chọn đề */
  .eo-status {
    margin-top: 0.4rem;
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--accent1);
  }
  .eo-status.done { color: var(--correct); }
  .eo-btn {
    background: var(--grad1);
    color: white;
    padding: 8px 16px;
    border-radius: 8px;
    font-size: 13px;
    font-weight: 600;
    font-family: 'Sora', sans-serif;
    border: none;
    cursor: pointer;
  }

  #exam-container {
    display: none;
  }
  
  .back-btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    color: var(--accent1);
    background: rgba(99,179,237,0.1);
    padding: 6px 12px;
    border-radius: 6px;
    font-size: 12px;
    font-weight: 600;
    cursor: pointer;
    border: 1px solid rgba(99,179,237,0.2);
    margin-bottom: 1.5rem;
    transition: background 0.2s;
  }
  .back-btn:hover { background: rgba(99,179,237,0.2); }