:root {
  --bg-primary: #ffffff;
  --bg-secondary: #f8f9fa;
  --bg-sidebar: #ffffff;
  --bg-selected: #f0f0f0;
  --text-primary: #1a1a1a;
  --text-secondary: #666666;
  --text-muted: #999999;
  --border-color: #e0e0e0;
  --accent-color: #2563eb;
  --accent-hover: #1d4ed8;
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1);
  --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.15);
  --border-radius: 8px;
  --sidebar-width: 300px;
  --transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg-primary: #0f0f0f;
    --bg-secondary: #1a1a1a;
    --bg-sidebar: #141414;
    --bg-selected: #2a2a2a;
    --text-primary: #e5e5e5;
    --text-secondary: #a0a0a0;
    --text-muted: #707070;
    --border-color: #2a2a2a;
    --accent-color: #3b82f6;
    --accent-hover: #60a5fa;
  }
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.app-container {
  display: flex;
  min-height: 100vh;
  max-width: 1600px;
  margin: 0 auto;
}

/* Sidebar */
.sidebar {
  width: var(--sidebar-width);
  background-color: var(--bg-sidebar);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
}

.sidebar-header {
  padding: 2rem 1.5rem;
  border-bottom: 1px solid var(--border-color);
}

.logo {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 1rem;
  letter-spacing: -0.5px;
}

.year-selector-wrapper {
  margin-top: 1rem;
}

.year-select {
  width: 100%;
  padding: 0.625rem 1rem;
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  background-color: var(--bg-secondary);
  color: var(--text-primary);
  font-size: 0.9375rem;
  font-family: inherit;
  cursor: pointer;
  transition: var(--transition);
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12' fill='none'%3E%3Cpath d='M3 4.5L6 7.5L9 4.5' stroke='%23666' stroke-width='1.5' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.75rem center;
  background-size: 12px;
  padding-right: 2.5rem;
}

.year-select:hover {
  border-color: var(--accent-color);
}

.year-select:focus {
  outline: none;
  border-color: var(--accent-color);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

/* Category Navigation */
.category-nav {
  flex: 1;
  padding: 1rem 0;
  overflow-y: auto;
}

.category-list {
  list-style: none;
  padding: 0;
}

.category-item {
  margin: 0.25rem 1rem;
  padding: 0.875rem 1rem;
  border-radius: var(--border-radius);
  cursor: pointer;
  transition: var(--transition);
  font-size: 0.9375rem;
  color: var(--text-primary);
  border: 1px solid transparent;
  position: relative;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.category-item:hover {
  background-color: var(--bg-secondary);
}

.category-item.active {
  background-color: var(--bg-selected);
  font-weight: 500;
}

.category-item::after {
  content: "›";
  color: var(--text-muted);
  font-size: 1.2rem;
  opacity: 0;
  transition: var(--transition);
}

.category-item:hover::after,
.category-item.active::after {
  opacity: 1;
}

.category-item.loading {
  cursor: default;
  color: var(--text-muted);
}

/* Main Content */
.main-content {
  flex: 1;
  display: flex;
  flex-direction: column;
  overflow-x: hidden;
  background-color: var(--bg-primary);
}

.content-header {
  padding: 2rem 2.5rem;
  border-bottom: 1px solid var(--border-color);
  background-color: var(--bg-primary);
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 2rem;
}

.category-title {
  font-size: 1.75rem;
  font-weight: 600;
  color: var(--text-primary);
  letter-spacing: -0.5px;
}

.header-actions {
  flex: 1;
  max-width: 600px;
}

.search-form {
  display: flex;
  gap: 0.75rem;
}

.search-input-wrapper {
  flex: 1;
  position: relative;
}

.search-form input {
  width: 100%;
  padding: 0.75rem 1rem;
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  background-color: var(--bg-secondary);
  color: var(--text-primary);
  font-size: 0.9375rem;
  font-family: inherit;
  transition: var(--transition);
}

.search-form input::placeholder {
  color: var(--text-muted);
}

.search-form input:focus {
  outline: none;
  border-color: var(--accent-color);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

/* Autocomplete Dropdown */
.autocomplete-dropdown {
  position: absolute;
  top: 100%;
  left: 0;
  right: 0;
  margin-top: 0.5rem;
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  box-shadow: var(--shadow-lg);
  max-height: 400px;
  overflow-y: auto;
  z-index: 1000;
  display: none;
}

.autocomplete-dropdown.visible {
  display: block;
}

.autocomplete-item {
  padding: 0.875rem 1rem;
  cursor: pointer;
  transition: var(--transition);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.autocomplete-item:last-child {
  border-bottom: none;
}

.autocomplete-item:hover,
.autocomplete-item.selected {
  background-color: var(--bg-secondary);
}

.autocomplete-item-title {
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--text-primary);
}

.autocomplete-item-meta {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 0.8125rem;
  color: var(--text-secondary);
}

.autocomplete-item-year {
  color: var(--accent-color);
  font-weight: 500;
}

.autocomplete-item-category {
  padding: 0.125rem 0.5rem;
  background-color: var(--bg-selected);
  border-radius: 4px;
  font-size: 0.75rem;
}

.search-form button {
  padding: 0.75rem 1.5rem;
  background-color: var(--accent-color);
  color: white;
  border: none;
  border-radius: var(--border-radius);
  font-size: 0.9375rem;
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition);
  white-space: nowrap;
}

.search-form button:hover {
  background-color: var(--accent-hover);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.search-form button:active {
  transform: translateY(0);
}

/* Papers Section */
.papers-section {
  flex: 1;
  padding: 2rem 2.5rem;
  overflow-y: auto;
}

.papers-section .section-title {
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--text-primary);
  margin: 0 0 1.5rem 0;
  letter-spacing: -0.5px;
}

.papers-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1.25rem;
}

.paper-card {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  padding: 1.5rem;
  cursor: pointer;
  transition: var(--transition);
  position: relative;
  overflow: hidden;
}

.paper-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 4px;
  height: 100%;
  background-color: var(--accent-color);
  transform: scaleY(0);
  transition: var(--transition);
}

.paper-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  border-color: var(--accent-color);
}

.paper-card:hover::before {
  transform: scaleY(1);
}

.paper-title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 0.5rem;
  line-height: 1.4;
}

.paper-meta {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 0.875rem;
  color: var(--text-secondary);
}

.paper-year {
  font-weight: 500;
  color: var(--accent-color);
}

.paper-category {
  padding: 0.25rem 0.625rem;
  background-color: var(--bg-selected);
  border-radius: 4px;
  font-size: 0.75rem;
}

/* Results Section */
.results-section {
  padding: 2rem 2.5rem;
  border-top: 1px solid var(--border-color);
  background-color: var(--bg-secondary);
  display: block;
}

.results-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
}

.result-section-card {
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
}

.section-header {
  background: linear-gradient(135deg, var(--accent-color) 0%, var(--accent-hover) 100%);
  color: white;
  padding: 1rem 1.5rem;
  font-size: 1rem;
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.results-body {
  max-height: 600px;
  overflow-y: auto;
  min-height: 200px;
}

.video-card,
.repo-card {
  display: flex;
  padding: 1rem 1.5rem;
  border-bottom: 1px solid var(--border-color);
  text-decoration: none;
  color: inherit;
  transition: var(--transition);
  gap: 1rem;
}

.video-card:hover,
.repo-card:hover {
  background-color: var(--bg-secondary);
  transform: translateX(4px);
}

.video-thumbnail {
  width: 160px;
  height: 90px;
  border-radius: var(--border-radius);
  overflow: hidden;
  flex-shrink: 0;
  background-color: var(--bg-secondary);
}

.video-thumbnail img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.video-details h3,
.repo-header h3 {
  font-size: 0.9375rem;
  font-weight: 600;
  margin-bottom: 0.375rem;
  color: var(--text-primary);
  line-height: 1.4;
}

.video-details p,
.repo-details p {
  font-size: 0.8125rem;
  color: var(--text-secondary);
  margin: 0.25rem 0;
}

.repo-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 0.5rem;
  gap: 1rem;
}

.repo-stats {
  display: flex;
  gap: 0.75rem;
  font-size: 0.8125rem;
  flex-shrink: 0;
}

.repo-stat {
  display: flex;
  align-items: center;
  gap: 0.25rem;
  color: var(--text-secondary);
}

.empty-state,
.loading-state {
  text-align: center;
  padding: 3rem 2rem;
  color: var(--text-muted);
  font-style: italic;
}

/* Loading Animation */
@keyframes pulse {
  0%,
  100% {
    opacity: 0.4;
  }
  50% {
    opacity: 1;
  }
}

.loading-dots {
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 2rem;
  gap: 0.5rem;
}

.pulse {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background-color: var(--accent-color);
  animation: pulse 1.5s infinite ease-in-out;
}

.pulse:nth-child(2) {
  animation-delay: 0.2s;
}

.pulse:nth-child(3) {
  animation-delay: 0.4s;
}

/* Error Banner */
.error-banner {
  margin: 1rem 1.5rem;
  padding: 0.875rem 1rem;
  border-radius: var(--border-radius);
  background-color: #fee;
  color: #c33;
  font-size: 0.875rem;
  border: 1px solid #fcc;
}

/* Responsive Design */
@media (max-width: 1024px) {
  .app-container {
    flex-direction: column;
  }

  .sidebar {
    width: 100%;
    height: auto;
    position: relative;
    border-right: none;
    border-bottom: 1px solid var(--border-color);
  }

  .sidebar-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
  }

  .logo {
    margin-bottom: 0;
  }

  .year-selector-wrapper {
    margin-top: 0;
    width: 150px;
  }

  .category-nav {
    max-height: 300px;
  }

  .category-list {
    display: flex;
    overflow-x: auto;
    padding: 0.5rem 0;
  }

  .category-item {
    white-space: nowrap;
    flex-shrink: 0;
    margin: 0 0.5rem;
  }

  .content-header {
    flex-direction: column;
    align-items: stretch;
    gap: 1rem;
  }

  .header-actions {
    max-width: 100%;
  }

  .results-layout {
    grid-template-columns: 1fr;
  }

  .papers-grid {
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
  }
}

@media (max-width: 640px) {
  .content-header,
  .papers-section,
  .results-section {
    padding: 1.5rem 1rem;
  }

  .category-title {
    font-size: 1.5rem;
  }

  .papers-grid {
    grid-template-columns: 1fr;
  }
}

/* Scrollbar Styling */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: var(--bg-secondary);
}

::-webkit-scrollbar-thumb {
  background: var(--border-color);
  border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--text-muted);
}