/* ===== Study Page Layout ===== */
.study-wrapper {
  display: grid;
  grid-template-columns: 210px 1fr;
  gap: 2.5rem;
  max-width: 1100px;
  margin: 0 auto;
  padding: 2.5rem 2rem;
  align-items: start;
}

/* ===== TOC Sidebar ===== */
.study-toc {
  position: sticky;
  top: 80px;
}

.toc-title {
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--text-secondary);
  margin-bottom: 0.75rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--border);
}

.toc-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.1rem;
}

.toc-list a {
  display: block;
  padding: 0.45rem 0.75rem;
  border-radius: 6px;
  font-size: 0.8rem;
  color: var(--text-secondary);
  text-decoration: none;
  transition: background 0.2s, color 0.2s, border-color 0.2s;
  border-left: 2px solid transparent;
  line-height: 1.4;
}

.toc-list a:hover {
  background: rgba(67, 97, 238, 0.08);
  color: var(--accent);
  border-left-color: var(--accent);
}

/* ===== Main Content ===== */
.study-content {
  min-width: 0;
}

/* ===== Section ===== */
.study-section {
  margin-bottom: 3rem;
  padding-bottom: 3rem;
  border-bottom: 1.5px solid var(--border);
  scroll-margin-top: 80px;
}

.study-section:last-child {
  border-bottom: none;
}

.study-h2 {
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 1.5rem;
  display: flex;
  align-items: center;
  gap: 0.65rem;
}

.study-h2::before {
  content: '';
  display: inline-block;
  width: 4px;
  height: 1.2em;
  background: linear-gradient(180deg, #4361ee, #4cc9f0);
  border-radius: 2px;
  flex-shrink: 0;
}

.study-h3 {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--accent);
  margin: 1.5rem 0 0.6rem;
}

.study-p {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.75;
  margin-bottom: 0.6rem;
}

/* ===== Info Grid ===== */
.info-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 0.9rem;
  margin-bottom: 1.5rem;
}

.info-card {
  background: var(--surface);
  border: 1.5px solid var(--border);
  border-radius: 12px;
  padding: 1.1rem 1.25rem;
  box-shadow: 0 2px 8px var(--shadow);
}

.info-card-label {
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 0.4rem;
}

.info-card-value {
  font-size: 0.88rem;
  color: var(--text-primary);
  line-height: 1.55;
}

/* ===== Grade Bars ===== */
.grade-list {
  display: flex;
  flex-direction: column;
  gap: 0.8rem;
  margin-bottom: 1.25rem;
}

.grade-item {
  display: flex;
  align-items: center;
  gap: 0.9rem;
}

.grade-label {
  font-size: 0.84rem;
  font-weight: 600;
  color: var(--text-primary);
  width: 130px;
  flex-shrink: 0;
}

.grade-track {
  flex: 1;
  height: 7px;
  background: var(--border);
  border-radius: 4px;
  overflow: hidden;
}

.grade-fill {
  height: 100%;
  width: var(--pct);
  border-radius: 4px;
  background: linear-gradient(90deg, #4361ee, #4cc9f0);
}

.grade-pct {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--accent);
  width: 32px;
  text-align: right;
  flex-shrink: 0;
}

/* ===== Highlight Box ===== */
.highlight-box {
  background: rgba(67, 97, 238, 0.06);
  border-left: 3px solid var(--accent);
  border-radius: 0 10px 10px 0;
  padding: 1rem 1.25rem;
  margin: 1rem 0;
  font-size: 0.88rem;
  color: var(--text-primary);
  line-height: 1.7;
}

.highlight-box strong {
  color: var(--accent);
}

.warn-box {
  background: rgba(234, 88, 12, 0.06);
  border-left: 3px solid #ea580c;
  border-radius: 0 10px 10px 0;
  padding: 1rem 1.25rem;
  margin: 1rem 0;
  font-size: 0.88rem;
  color: var(--text-primary);
  line-height: 1.7;
}

.warn-box strong { color: #ea580c; }

/* ===== Key Points List ===== */
.key-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  margin: 0.5rem 0 0.75rem;
}

.key-list li {
  display: flex;
  align-items: flex-start;
  gap: 0.55rem;
  font-size: 0.88rem;
  color: var(--text-primary);
  line-height: 1.6;
}

.key-list li::before {
  content: '▸';
  color: var(--accent);
  font-size: 0.75em;
  margin-top: 0.25em;
  flex-shrink: 0;
}

/* ===== Code Blocks ===== */
.code-block {
  background: #0d1117;
  border: 1px solid #30363d;
  border-radius: 10px;
  overflow: hidden;
  margin: 1rem 0;
  font-size: 0;
}

.code-label {
  display: block;
  background: #161b22;
  padding: 0.45rem 1rem;
  font-size: 0.72rem;
  font-weight: 600;
  color: #8b949e;
  border-bottom: 1px solid #30363d;
  letter-spacing: 0.05em;
}

.code-block pre {
  margin: 0;
  padding: 1.1rem 1.25rem;
  font-family: 'Fira Code', 'Courier New', monospace;
  font-size: 0.82rem;
  line-height: 1.65;
  color: #e6edf3;
  overflow-x: auto;
}

/* ===== Code Compare (2-column) ===== */
.code-compare {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  margin: 1rem 0;
}

/* ===== Concept Compare Table ===== */
.compare-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.88rem;
  margin: 1rem 0;
  border: 1.5px solid var(--border);
  border-radius: 10px;
  overflow: hidden;
}

.compare-table th {
  background: var(--nav-bg);
  color: #ffffff;
  padding: 0.65rem 1rem;
  text-align: left;
  font-weight: 600;
  font-size: 0.82rem;
}

.compare-table td {
  padding: 0.75rem 1rem;
  border-top: 1px solid var(--border);
  color: var(--text-primary);
  vertical-align: top;
  line-height: 1.55;
}

.compare-table tr:nth-child(even) td {
  background: rgba(67, 97, 238, 0.03);
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .study-wrapper {
    grid-template-columns: 1fr;
    padding: 1.5rem 1rem;
    gap: 1.5rem;
  }

  .study-toc {
    position: static;
    background: var(--surface);
    border: 1.5px solid var(--border);
    border-radius: 10px;
    padding: 1rem;
  }

  .toc-list {
    flex-direction: row;
    flex-wrap: wrap;
    gap: 0.35rem;
  }

  .toc-list a {
    border-left: none;
    border-radius: 20px;
    border: 1px solid var(--border);
    padding: 0.3rem 0.75rem;
    white-space: nowrap;
  }

  .code-compare {
    grid-template-columns: 1fr;
  }
}