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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: #181a21;
  color: #e0e0e0;
  min-height: 100vh;
  line-height: 1.6;
}

.layout {
  display: flex;
  min-height: 100vh;
}

/* Sidebar */
.sidebar {
  width: 240px;
  background: #1e2029;
  border-right: 1px solid #2a2d38;
  padding: 20px 0;
  position: fixed;
  top: 0;
  left: 0;
  height: 100vh;
  z-index: 100;
  transition: transform 0.3s ease;
  overflow-y: auto;
}

.sidebar-top {
  padding: 16px 16px 20px;
  border-bottom: 1px solid #2a2d38;
}

.btn-back-site {
  display: block;
  width: 100%;
  padding: 12px 16px;
  background: linear-gradient(135deg, #ff8c00, #ff6a00);
  color: #fff;
  font-size: 14px;
  font-weight: 600;
  text-align: center;
  text-decoration: none;
  border-radius: 8px;
  transition: opacity 0.2s;
}

.btn-back-site:hover {
  opacity: 0.85;
  color: #fff;
}

.top-bar {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  padding: 12px 20px;
}

.btn-back-top {
  padding: 8px 16px;
  background: linear-gradient(135deg, #ff8c00, #ff6a00);
  color: #fff;
  font-size: 14px;
  font-weight: 600;
  text-decoration: none;
  border-radius: 6px;
  transition: opacity 0.2s;
}

.btn-back-top:hover {
  opacity: 0.85;
  color: #fff;
}

.sidebar-nav { padding: 16px 12px; }

.nav-section-title {
  font-size: 11px;
  color: #666;
  text-transform: uppercase;
  padding: 12px 12px 6px;
  letter-spacing: 1px;
}

.nav-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 12px;
  border-radius: 8px;
  color: #a0a0a0;
  text-decoration: none;
  font-size: 14px;
  transition: all 0.2s;
  margin-bottom: 2px;
}

.nav-item:hover { background: #262833; color: #fff; }
.nav-item.active { background: rgba(25, 114, 245, 0.15); color: #4d9aff; }
.nav-icon { font-size: 16px; }

/* Main Content */
.main-content {
  flex: 1;
  margin-left: 240px;
  min-width: 0;
  position: relative;
}

.menu-toggle {
  display: none;
  position: fixed;
  top: 12px;
  left: 12px;
  z-index: 90;
  background: #1e2029;
  border: 1px solid #2a2d38;
  border-radius: 8px;
  color: #e0e0e0;
  font-size: 20px;
  width: 40px;
  height: 40px;
  cursor: pointer;
}

.page-title { font-size: 16px; font-weight: 600; color: #fff; }

/* Hero */
.hero {
  background: linear-gradient(135deg, #1a3a6b 0%, #2d1b69 100%);
  margin: 16px;
  border-radius: 12px;
  overflow: hidden;
}

.hero-overlay {
  padding: 48px 32px;
  background: rgba(0, 0, 0, 0.15);
}

.hero-overlay h2 { font-size: 26px; font-weight: 700; color: #fff; margin-bottom: 8px; }
.hero-overlay p { font-size: 14px; color: rgba(255, 255, 255, 0.7); }

/* Platform Tabs */
.platform-tabs {
  display: flex;
  gap: 8px;
  padding: 20px 24px 0;
  flex-wrap: wrap;
}

.tab-btn {
  padding: 10px 20px;
  border: 1px solid #2a2d38;
  border-radius: 8px;
  background: #1e2029;
  color: #a0a0a0;
  font-size: 14px;
  cursor: pointer;
  transition: all 0.2s;
}

.tab-btn:hover { border-color: #4d9aff; color: #fff; }
.tab-btn.active { background: rgba(25, 114, 245, 0.15); border-color: #4d9aff; color: #4d9aff; }

/* Tutorials */
.tutorials { padding: 20px 24px 40px; }
.tutorial-panel { display: none; }
.tutorial-panel.active { display: block; }
.category-title h2 { font-size: 20px; font-weight: 600; color: #fff; margin-bottom: 8px; }
.subtitle { font-size: 14px; color: #888; margin-bottom: 20px; }

/* Notice boxes */
.notice {
  border-radius: 8px;
  padding: 14px 18px;
  margin-bottom: 20px;
  font-size: 14px;
}

.notice.warning {
  background: rgba(255, 152, 0, 0.08);
  border: 1px solid rgba(255, 152, 0, 0.3);
}

.notice.warning strong { color: #ffb74d; }

.notice.info {
  background: rgba(25, 114, 245, 0.08);
  border: 1px solid rgba(25, 114, 245, 0.25);
}

.notice p { margin-top: 4px; color: #ccc; }

/* Step Cards */
.step-card {
  background: #1e2029;
  border: 1px solid #2a2d38;
  border-radius: 12px;
  margin-bottom: 20px;
  overflow: hidden;
}

.step-header {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 18px 24px;
  border-bottom: 1px solid #2a2d38;
}

.step-number {
  width: 30px;
  height: 30px;
  border-radius: 50%;
  background: rgba(25, 114, 245, 0.2);
  color: #4d9aff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 14px;
  flex-shrink: 0;
}

.step-header h3 { font-size: 16px; font-weight: 600; color: #fff; }

.step-body {
  padding: 20px 24px;
}

.step-body p { margin-bottom: 12px; font-size: 14px; color: #ccc; }
.step-body h4 { font-size: 15px; color: #fff; margin: 20px 0 8px; }
.step-body code {
  background: #262833;
  padding: 2px 8px;
  border-radius: 4px;
  font-size: 13px;
  color: #4d9aff;
}

/* Images */
.step-body img {
  max-width: 100%;
  height: auto;
  border-radius: 8px;
  border: 1px solid #2a2d38;
  margin: 8px 0 16px;
  display: block;
}

.img-grid {
  display: grid;
  grid-template-columns: 1fr 2fr 1.5fr;
  gap: 12px;
  margin: 12px 0 16px;
  max-width: 780px;
}

.img-grid img {
  width: 100%;
  height: auto;
  margin: 0;
}

.img-grid img:first-child {
  max-width: 180px;
}

/* Download Links */
.download-links {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  margin: 12px 0 16px;
}

.btn-download {
  display: inline-block;
  padding: 10px 20px;
  background: rgba(25, 114, 245, 0.15);
  border: 1px solid rgba(25, 114, 245, 0.4);
  border-radius: 8px;
  color: #4d9aff;
  text-decoration: none;
  font-size: 14px;
  font-weight: 500;
  transition: all 0.2s;
}

.btn-download:hover {
  background: rgba(25, 114, 245, 0.25);
  border-color: #4d9aff;
}

.btn-download.btn-sm { padding: 6px 14px; font-size: 13px; }

/* FAQ / Details */
.faq-mini { margin: 16px 0; }

.faq-mini details {
  background: #262833;
  border-radius: 8px;
  margin-bottom: 8px;
  overflow: hidden;
}

.faq-mini summary {
  padding: 12px 16px;
  cursor: pointer;
  font-size: 14px;
  color: #ccc;
  font-weight: 500;
  list-style: none;
}

.faq-mini summary::-webkit-details-marker { display: none; }
.faq-mini summary::before { content: "▸ "; color: #4d9aff; }
.faq-mini details[open] summary::before { content: "▾ "; }

.details-body {
  padding: 0 16px 16px;
  font-size: 14px;
  color: #aaa;
}

.details-body a { color: #4d9aff; }

/* FAQ Cards */
.faq-cards { display: flex; flex-direction: column; gap: 16px; }

.faq-card {
  background: #1e2029;
  border: 1px solid #2a2d38;
  border-radius: 12px;
  overflow: hidden;
}

.faq-question {
  padding: 18px 22px;
  font-size: 15px;
  font-weight: 600;
  color: #fff;
  border-bottom: 1px solid #2a2d38;
  background: #232530;
}

.faq-question::before {
  content: "Q";
  display: inline-block;
  width: 24px;
  height: 24px;
  line-height: 24px;
  text-align: center;
  border-radius: 6px;
  background: rgba(25, 114, 245, 0.2);
  color: #4d9aff;
  font-size: 12px;
  font-weight: 700;
  margin-right: 12px;
  vertical-align: middle;
}

.faq-answer {
  padding: 18px 22px;
  font-size: 14px;
  color: #bbb;
  line-height: 1.7;
}

.faq-answer h4 { color: #fff; margin: 14px 0 6px; font-size: 14px; }
.faq-answer h4:first-child { margin-top: 0; }
.faq-answer p { margin-bottom: 10px; }
.faq-answer ul, .faq-answer ol { padding-left: 20px; margin-bottom: 10px; }
.faq-answer li { margin-bottom: 4px; }
.faq-answer code {
  background: #262833;
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 13px;
  color: #4d9aff;
}

/* Mode Compare */
.mode-compare {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin: 12px 0 16px;
}

.mode-item {
  background: #262833;
  border-radius: 8px;
  padding: 16px;
}

.mode-item strong { color: #fff; font-size: 14px; }
.mode-item p { font-size: 13px; color: #999; margin-top: 6px; }

/* Misc */
.text-muted { color: #888 !important; font-size: 13px !important; }
.text-muted a { color: #4d9aff; }
a { color: #4d9aff; text-decoration: none; }

/* Responsive */
@media (max-width: 768px) {
  .sidebar { transform: translateX(-100%); }
  .sidebar.open { transform: translateX(0); }
  .main-content { margin-left: 0; }
  .menu-toggle { display: block; position: static; }
  .top-bar { justify-content: space-between; }
  .hero { margin: 10px; }
  .hero-overlay { padding: 32px 20px; }
  .hero-overlay h2 { font-size: 20px; }
  .platform-tabs { padding: 16px 16px 0; }
  .tutorials { padding: 16px; }
  .step-header { padding: 14px 16px; }
  .step-body { padding: 16px; }
  .img-grid { grid-template-columns: 1fr; }
  .mode-compare { grid-template-columns: 1fr; }
  .tab-btn { padding: 8px 14px; font-size: 13px; }
}