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

:root {
  --primary-dark: #1a1a2e;
  --secondary-dark: #16213e;
  --accent-blue: #0f3460;
  --primary-color: #e94560;
  --secondary-color: #f39c12;
  --text-light: #ecf0f1;
  --text-muted: #bdc3c7;
  --success-color: #27ae60;
}

html {
  font-size: 16px;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', sans-serif;
  background: linear-gradient(135deg, var(--primary-dark) 0%, var(--secondary-dark) 100%);
  color: var(--text-light);
  min-height: 100vh;
}

.papers-header {
  background: linear-gradient(135deg, #1a1a2e 0%, #0f3460 100%);
  border-bottom: 3px solid var(--primary-color);
  padding: 3rem 1rem;
  text-align: center;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
}

.papers-header h1 {
  font-size: 2.5rem;
  margin-bottom: 0.5rem;
  color: var(--text-light);
}

.header-subtitle {
  font-size: 1.125rem;
  color: var(--text-muted);
  margin-bottom: 1rem;
}

.updated-at {
  font-size: 0.9rem;
  color: var(--secondary-color);
}

.papers-wrapper {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 2rem;
  max-width: 1400px;
  margin: 2rem auto;
  padding: 0 1rem;
}

.papers-filters {
  background: rgba(15, 52, 96, 0.3);
  border: 1px solid rgba(233, 69, 96, 0.2);
  border-radius: 0.5rem;
  padding: 1.5rem;
  height: fit-content;
  position: sticky;
  top: 1rem;
}

.filter-group {
  margin-bottom: 1.5rem;
}

.filter-group:last-of-type {
  margin-bottom: 1rem;
}

.filter-group h3 {
  font-size: 1rem;
  margin-bottom: 0.75rem;
  color: var(--secondary-color);
  border-bottom: 1px solid rgba(243, 156, 18, 0.3);
  padding-bottom: 0.5rem;
}

.search-input {
  width: 100%;
  padding: 0.75rem;
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 0.5rem;
  color: var(--text-light);
  font-size: 0.95rem;
  transition: all 0.3s ease;
}

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

.search-input:focus {
  outline: none;
  border-color: var(--primary-color);
  background: rgba(255, 255, 255, 0.08);
  box-shadow: 0 0 0 3px rgba(233, 69, 96, 0.2);
}

#searchHint {
  display: block;
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-top: 0.5rem;
}

.category-list {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.category-option {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.5rem;
  cursor: pointer;
  border-radius: 0.25rem;
  transition: all 0.2s ease;
  font-size: 0.95rem;
}

.category-option:hover {
  background: rgba(233, 69, 96, 0.1);
}

.category-checkbox {
  width: 18px;
  height: 18px;
  cursor: pointer;
  accent-color: var(--primary-color);
}

.sort-select {
  width: 100%;
  padding: 0.75rem;
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 0.5rem;
  color: var(--text-light);
  font-size: 0.95rem;
  cursor: pointer;
  transition: all 0.3s ease;
}

.sort-select:focus {
  outline: none;
  border-color: var(--primary-color);
  background: rgba(255, 255, 255, 0.08);
}

.sort-select option {
  background: var(--secondary-dark);
  color: var(--text-light);
}

.papers-container {
  min-height: 400px;
}

.state-message {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 3rem;
  text-align: center;
  background: rgba(15, 52, 96, 0.3);
  border: 1px solid rgba(233, 69, 96, 0.2);
  border-radius: 0.5rem;
  min-height: 300px;
}

.state-message p {
  margin: 1rem 0;
  font-size: 1.125rem;
}

.state-message.error p {
  color: #e74c3c;
}

.spinner {
  border: 4px solid rgba(233, 69, 96, 0.2);
  border-top-color: var(--primary-color);
  border-radius: 50%;
  width: 40px;
  height: 40px;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

.papers-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
  gap: 1.5rem;
  margin-bottom: 2rem;
}

.paper-card {
  background: rgba(15, 52, 96, 0.3);
  border: 1px solid rgba(233, 69, 96, 0.2);
  border-radius: 0.75rem;
  padding: 1.5rem;
  transition: all 0.3s ease;
  display: flex;
  flex-direction: column;
}

.paper-card:hover {
  border-color: var(--primary-color);
  background: rgba(15, 52, 96, 0.5);
  box-shadow: 0 8px 30px rgba(233, 69, 96, 0.2);
  transform: translateY(-4px);
}

.paper-card__header {
  margin-bottom: 1rem;
}

.paper-card__title {
  font-size: 1.125rem;
  margin-bottom: 0.5rem;
  line-height: 1.4;
}

.paper-card__title a {
  color: var(--text-light);
  text-decoration: none;
  transition: color 0.3s ease;
}

.paper-card__title a:hover {
  color: var(--secondary-color);
}

.paper-card__arxiv-id {
  display: inline-block;
  background: rgba(243, 156, 18, 0.1);
  color: var(--secondary-color);
  padding: 0.25rem 0.75rem;
  border-radius: 0.25rem;
  font-size: 0.85rem;
  font-weight: 600;
}

.paper-card__metadata {
  margin-bottom: 1rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.paper-card__authors,
.paper-card__date {
  font-size: 0.9rem;
  margin-bottom: 0.5rem;
  color: var(--text-muted);
}

.paper-card__authors strong {
  color: var(--text-light);
}

.paper-card__date {
  color: var(--secondary-color);
}

.paper-card__categories {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
}

.category-tag {
  display: inline-block;
  background: rgba(15, 52, 96, 0.5);
  border: 1px solid rgba(233, 69, 96, 0.3);
  color: var(--text-muted);
  padding: 0.3rem 0.75rem;
  border-radius: 0.25rem;
  font-size: 0.8rem;
}

.paper-card__abstract {
  flex: 1;
  font-size: 0.95rem;
  line-height: 1.6;
  color: var(--text-muted);
  margin-bottom: 1rem;
}

.paper-card__actions {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.75rem;
}

.btn {
  padding: 0.75rem 1rem;
  border: none;
  border-radius: 0.5rem;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.3s ease;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  text-align: center;
}

.btn-pdf,
.btn-arxiv {
  background: rgba(233, 69, 96, 0.2);
  color: var(--text-light);
  border: 1px solid rgba(233, 69, 96, 0.4);
}

.btn-pdf:hover,
.btn-arxiv:hover {
  background: var(--primary-color);
  border-color: var(--primary-color);
}

.btn-secondary {
  background: transparent;
  color: var(--secondary-color);
  border: 1px solid var(--secondary-color);
}

.btn-secondary:hover {
  background: rgba(243, 156, 18, 0.1);
}

.btn-primary {
  background: var(--primary-color);
  color: white;
  border: none;
}

.btn-primary:hover {
  background: #c0234e;
}

.pagination {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1rem;
  margin-top: 2rem;
  padding: 1.5rem;
  background: rgba(15, 52, 96, 0.3);
  border-radius: 0.5rem;
}

.page-info {
  padding: 0 1rem;
  color: var(--secondary-color);
  font-weight: 600;
}

.papers-footer {
  text-align: center;
  padding: 2rem 1rem;
  color: var(--text-muted);
  border-top: 1px solid rgba(233, 69, 96, 0.2);
  margin-top: 3rem;
}

.papers-footer a {
  color: var(--secondary-color);
  text-decoration: none;
  transition: color 0.3s ease;
}

.papers-footer a:hover {
  color: var(--primary-color);
  text-decoration: underline;
}

@media (max-width: 1024px) {
  .papers-wrapper {
    grid-template-columns: 1fr;
  }

  .papers-filters {
    position: static;
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1rem;
  }

  .filter-group {
    margin-bottom: 0;
  }

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

@media (max-width: 768px) {
  .papers-header {
    padding: 2rem 1rem;
  }

  .papers-header h1 {
    font-size: 1.75rem;
  }

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

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

  .paper-card__actions {
    grid-template-columns: 1fr;
  }

  .pagination {
    flex-wrap: wrap;
  }
}

@media (max-width: 480px) {
  .papers-header {
    padding: 1.5rem 1rem;
  }

  .papers-header h1 {
    font-size: 1.5rem;
  }

  .papers-wrapper {
    gap: 1rem;
    padding: 0 0.5rem;
  }

  .papers-filters {
    padding: 1rem;
  }

  .filter-group h3 {
    font-size: 0.95rem;
  }

  .state-message {
    padding: 1.5rem;
    min-height: 250px;
  }

  .papers-grid {
    gap: 1rem;
  }

  .paper-card {
    padding: 1rem;
  }

  .btn {
    padding: 0.65rem 0.85rem;
    font-size: 0.85rem;
  }
}