:root {
  --primary: #003366;
  --primary-light: #005a9c;
  --text-dark: #1e293b;
  --text-gray: #64748b;
  --bg-page: #f8fafc;
  --card-bg: #ffffff;
  --code-bg: #f1f5f9;
  --code-border: #e2e8f0;
  --border: #e2e8f0;
  --shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
  --radius-md: 12px;
  --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --spacing-lg: 40px;
  --spacing-md: 24px;
  --spacing-sm: 16px;
}

body {
  color: var(--text-dark);
  line-height: 1.7;
  font:13px Courier, Geneva, sans-serif,serif;
  background-color: var(--bg-page);
  max-width: 960px;
  margin: 0 auto;
  min-height: 100vh;
}

.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 20px;
}

header {
  text-align: center;
  padding: var(--spacing-lg) 0 var(--spacing-md);
}

h1 {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--primary);
  letter-spacing: -0.025em;
  margin-bottom: 12px;
}

.subtitle {
  font-size: 1.15rem;
  color: var(--text-gray);
  max-width: 700px;
  margin: 0 auto;
  opacity: 0.9;
}

.tutorial-content {
  margin: var(--spacing-md) 0;
  line-height: 1.8;
}

.section {
  margin-bottom: var(--spacing-md);
}

h2 {
  font-size: 1.5rem;
  color: var(--primary);
  margin-bottom: 12px;
  font-weight: 600;
}

h3 {
  font-size: 1.3rem;
  color: var(--primary-light);
  margin: 16px 0 8px;
  font-weight: 600;
}

li::marker {
  color: var(--primary-light);
}

.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 16px;
  margin: var(--spacing-sm) 0;
}

.feature-card {
  background: var(--card-bg);
  border-radius: var(--radius-md);
  padding: 16px;
  box-shadow: var(--shadow);
  border: 1px solid var(--border);
  transition: var(--transition);
}

.feature-card:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.12);
}

.feature-icon {
  color: var(--primary-light);
  font-size: 1.5rem;
  margin-bottom: 8px;
}

.feature-card h4 {
  font-size: 1.15rem;
  color: var(--primary);
  margin-bottom: 8px;
}

table {
  width: 100%;
  border-collapse: collapse;
  margin: var(--spacing-sm) 0;
  background: var(--card-bg);
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: var(--shadow);
  border: 1px solid var(--border);
}

th, td {
  padding: 12px 16px;
  text-align: left;
  border-bottom: 1px solid var(--border);
}

th {
  background-color: var(--primary);
  color: white;
  font-weight: 600;
}

tr:last-child td {
  border-bottom: none;
}

.code-card {
  background: var(--card-bg);
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: var(--shadow);
  margin: var(--spacing-sm) 0;
  border: 1px solid var(--border);
}

.code-header {
  background-color: var(--primary);
  color: white;
  padding: 12px 16px;
  font-size: 1.1rem;
  font-weight: 500;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.code-body {
  padding: 0;
  overflow-x: auto;
  background-color: var(--code-bg);
}

pre {
  margin: 0;
  padding: 16px;
  background-color: var(--code-bg);
  color: #2d3748;
  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
  font-size: 0.95rem;
  line-height: 1.5;
  direction: ltr;
  text-align: left;
  white-space: pre;
  word-spacing: normal;
  word-break: normal;
}

code {
  font-family: inherit;
  background: #e9ecef;
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 0.95em;
}
.hl-tag { color: #268bd2; }
.hl-attr { color: #cb4b16; }
.hl-value { color: #2aa198; }
.hl-comment { color: #657b83; font-style: italic; }
.hl-keyword { color: #859900; font-weight: bold; }
.hl-type { color: #cb4b16; }
.hl-function { color: #268bd2; }
.hl-string { color: #2aa198; }
.hl-preprocessor { color: #d33682; }
.hl-variable { color: #b58900; }
.hl-error { color: #dc3545; }
.hl-number { color: #d33682; }
.hl-key { color: #d33682; font-weight: bold; }
.hl-scheme { color: #268bd2; font-weight: bold; }
.hl-host { color: #2aa198; }
.hl-port { color: #cb4b16; }
.hl-path { color: #859900; }
.hl-param { color: #d33682; }
.hl-value { color: #2aa198; }
.hl-command { color: #268bd2; font-weight: bold; }
.hl-sdp-field { color: #268bd2; font-weight: bold; }
.hl-sdp-attr { color: #cb4b16; }
.hl-sdp-crypto { color: #d33682; }
.hl-sdp-key { color: #859900; }
.hl-protocol { color: #cb4b16; }
.hl-crypto { color: #859900; }
.hl-method { color: #859900; }

.diagram {
  background: var(--card-bg);
  border-radius: var(--radius-md);
  padding: 20px;
  margin: var(--spacing-sm) 0;
  border: 1px dashed var(--border);
  text-align: center;
  font-style: italic;
  color: var(--text-gray);
}

.param-table,
.mode-table,
.method-table {
  width: 100%;
  border-collapse: collapse;
  margin: var(--spacing-sm) 0;
}

.param-table th,
.param-table td,
.mode-table th,
.mode-table td,
.method-table th,
.method-table td {
  border: 1px solid var(--border);
  padding: 12px;
  text-align: left;
}

.param-table th,
.mode-table th,
.method-table th {
  background-color: var(--primary);
  color: white;
}

.param-table tr:nth-child(even),
.mode-table tr:nth-child(even),
.method-table tr:nth-child(even) {
  background-color: var(--code-bg);
}

.security-note {
  background-color: #fffbeb;
  border-left: 4px solid #f59e0b;
  padding: 16px;
  margin: var(--spacing-sm) 0;
  border-radius: 0 8px 8px 0;
  font-size: 0.95rem;
}

.note {
  background-color: #fffbeb;
  border-left: 4px solid #f59e0b;
  padding: 12px 16px;
  margin: 12px 0;
  border-radius: 0 8px 8px 0;
  font-size: 0.95rem;
  color: #7c2d12;
}

.warning {
  background-color: #fee2e2;
  border-left: 4px solid #ef4444;
  padding: 16px;
  margin: var(--spacing-sm) 0;
  border-radius: 0 8px 8px 0;
  font-size: 0.95rem;
}

.param-category {
  background: var(--card-bg);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow);
  padding: 16px;
  margin: 12px 0;
  border: 1px solid var(--border);
}

.category-title {
  font-weight: 600;
  color: var(--primary-light);
  margin-bottom: 8px;
  font-size: 1.1rem;
}

.param-list {
  list-style: none;
  margin: 0;
  padding: 0 0 0 16px;
}

.param-item {
  margin-bottom: 8px;
  color: var(--text-gray);
}

.param-key {
  font-weight: 500;
  color: var(--primary);
  font-family: 'SFMono-Regular', monospace;
}

.param-values {
  display: inline-block;
  margin: 4px 0;
  padding: 2px 6px;
  background-color: var(--code-bg);
  border-radius: 4px;
  font-family: 'SFMono-Regular', monospace;
  font-size: 0.85rem;
  color: #cb4b16;
}

.param-desc {
  font-size: 0.95rem;
  margin-left: 8px;
}

@media (max-width: 768px) {
  h1 { font-size: 2rem; }
  .subtitle { font-size: 1rem; }
  .code-header { font-size: 1rem; }
  pre { padding: 12px; font-size: 0.85rem; }
  th, td { padding: 8px 12px; }
  .param-list { padding-left: 12px; }
  .param-table th, .param-table td, .mode-table th, .mode-table td, .method-table th, .method-table td { padding: 8px; }
}