/* Layout Structure */
.container {
  display: flex;
  min-height: 100vh;
}

/* Sidebar */
.sidebar {
  width: 320px;
  background: #ffffff;
  color: #111;
  padding: 0 20px;
  position: fixed;
  left: 260px;
  top: 0;
  height: 100vh;
  overflow-y: auto;
  z-index: 100;
}

.sidebar-content {
  display: flex;
  flex-direction: column;
  height: 100%;
  justify-content: center;
}

/* Navigation */
.sidebar-nav {
  margin-bottom: 0;
}

.nav-item {
  display: block;
  padding: 8px 0;
  font-size: 13px;
  font-weight: 500;
  color: #666;
  cursor: pointer;
  transition: all 0.3s ease;
  border-left: 2px solid transparent;
  padding-left: 12px;
  text-decoration: none;
}

.nav-item:hover {
  opacity: 1;
  color: #111;
}

.nav-item.active {
  opacity: 1;
  color: #111;
  border-left-color: #111;
}

.nav-number {
  font-weight: 700;
  color: #999;
  margin-right: 8px;
}

/* Mobile Menu Toggle */
.mobile-menu-toggle {
  display: none;
  position: fixed;
  top: 20px;
  left: 180px;
  z-index: 200;
  background: #ffffff;
  border: 1px solid #e0e0e0;
  color: #111;
  font-size: 24px;
  cursor: pointer;
  padding: 10px;
  border-radius: 4px;
}

/* Main Content Area */
.main-content {
  margin-left: 660px;
  flex: 1;
  background: #ffffff;
}

.content-inner {
  max-width: 900px;
  padding: 80px 60px;
  margin: 0 auto;
}

/* Controls */
.controls {
  display: flex;
  gap: 12px;
  margin-bottom: 32px;
}

.btn {
  padding: 8px 16px;
  border: 1px solid #e0e0e0;
  background: #fff;
  color: #666;
  font-family: 'Circular Std', sans-serif;
  font-size: 12px;
  font-weight: 500;
  cursor: pointer;
  border-radius: 2px;
  transition: all 0.2s ease;
}

.btn:hover {
  background: #f5f5f5;
  color: #111;
}

/* Section Styles */
.section {
  margin-bottom: 32px;
  border-bottom: 1px solid #e0e0e0;
  padding-bottom: 28px;
}

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

.section-header {
  display: flex;
  align-items: flex-start;
  gap: 20px;
  cursor: pointer;
  user-select: none;
  margin-bottom: 0;
  padding: 20px 0;
  transition: background 0.2s ease;
}

.section-header:hover {
  opacity: 0.85;
}

.section-number {
  font-size: 32px;
  font-weight: 400;
  color: #999;
  line-height: 1;
  min-width: 48px;
}

.section-header-content {
  flex: 1;
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 20px;
}

.section-title {
  font-size: 18px;
  font-weight: 700;
  color: #111;
  line-height: 1.3;
}

.section-toggle {
  font-size: 20px;
  font-weight: 400;
  color: #999;
  cursor: pointer;
  user-select: none;
  line-height: 1;
  flex-shrink: 0;
  transition: transform 0.3s ease;
}

.section-body {
  display: none;
  padding-left: 48px;
  padding-top: 20px;
}

.section-body.visible {
  display: block;
}

.section-body p {
  font-size: 15px;
  line-height: 1.7;
  margin-bottom: 20px;
  color: #333;
}

/* Resource Card Styles */
.resource-card {
  margin-bottom: 40px;
  padding-bottom: 40px;
  border-bottom: 1px solid #f0f0f0;
}

.resource-card:last-child {
  border-bottom: none;
  margin-bottom: 0;
  padding-bottom: 0;
}

.resource-name {
  font-size: 18px;
  font-weight: 700;
  color: #111;
  margin-bottom: 8px;
  line-height: 1.3;
}

.resource-name a {
  color: #111;
  text-decoration: none;
  transition: opacity 0.2s ease;
}

.resource-name a:hover {
  opacity: 0.6;
}

.resource-url {
  font-size: 12px;
  font-weight: 400;
  color: #999;
  margin-bottom: 12px;
  letter-spacing: 0.3px;
}

.resource-url a {
  color: #999;
  text-decoration: none;
}

.resource-url a:hover {
  color: #111;
}

.resource-desc {
  font-size: 15px;
  line-height: 1.7;
  color: #333;
}

/* Responsive Design */
@media (max-width: 900px) {
  .sidebar {
    left: 0;
    width: 320px;
    padding: 60px 40px;
  }

  .main-content {
    margin-left: 0;
  }

  .mobile-menu-toggle {
    left: 20px;
  }
}

@media (max-width: 768px) {
  .sidebar {
    width: 320px;
    height: auto;
    position: fixed;
    top: 48px;
    left: 0;
    transform: translateX(-100%);
    transition: transform 0.3s ease;
    padding: 60px 40px;
    z-index: 150;
    max-height: 100vh;
  }

  .sidebar.open {
    transform: translateX(0);
  }

  .mobile-menu-toggle {
    display: block;
    left: 20px;
  }

  .main-content {
    margin-left: 0;
  }

  .content-inner {
    padding: 40px 24px;
    padding-top: 60px;
  }

  .section-number {
    font-size: 24px;
    min-width: 36px;
  }

  .section-title {
    font-size: 16px;
  }

  .section-body {
    padding-left: 32px;
  }

  .controls {
    flex-direction: column;
  }

  .btn {
    width: 100%;
  }
}