.papers-hero {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 12px;
  margin-bottom: 16px;
  padding: 18px 20px;
}

.papers-hero h1 {
  margin: 0;
  font-size: 24px;
}

.papers-hero p {
  margin: 6px 0 0;
  color: var(--muted);
}

.papers-hero-actions {
  display: flex;
  gap: 8px;
  align-items: center;
}

.papers-wrap {
  display: grid;
  gap: 16px;
}

.papers-filters {
  padding: 16px;
}

.papers-filters h2 {
  margin: 0 0 14px;
  font-size: 18px;
}

.papers-controls-grid {
  display: grid;
  grid-template-columns: repeat(6, minmax(120px, 1fr));
  gap: 10px;
}

.filter-input {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 10px 12px;
  background: var(--surface);
  color: var(--text);
}

.semester-chips {
  display: flex;
  gap: 8px;
  margin-top: 12px;
}

.papers-counter {
  margin: 12px 0 0;
  color: var(--muted);
}

#papersContainer {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 14px;
}

.paper-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 14px;
  box-shadow: var(--shadow);
  overflow: hidden;
}

.paper-card-head {
  padding: 14px;
  border-bottom: 1px solid var(--border);
}

.paper-card-head h3 {
  margin: 0;
  font-size: 16px;
}

.paper-card-body {
  padding: 14px;
}

.paper-meta-row {
  display: flex;
  justify-content: space-between;
  color: var(--muted);
  font-size: 13px;
  margin-bottom: 8px;
}

.paper-actions {
  display: flex;
  gap: 8px;
  margin-top: 14px;
}

.paper-actions .outline-btn,
.paper-actions .primary-btn {
  flex: 1;
  text-align: center;
  text-decoration: none;
}

@media (max-width: 980px) {
  .papers-controls-grid {
    grid-template-columns: repeat(2, minmax(150px, 1fr));
  }
}

@media (max-width: 640px) {
  .papers-controls-grid {
    grid-template-columns: 1fr;
  }

  .papers-hero-actions {
    width: 100%;
  }

  .papers-hero-actions .outline-btn,
  .papers-hero-actions .primary-btn {
    flex: 1;
    text-align: center;
  }
}

/* Filter Toggle Styles */
.papers-filter-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 0;
}

.papers-filters h2 {
  margin: 0;
  font-size: 18px;
}

.filter-toggle-btn {
  background: none;
  border: none;
  font-size: 18px;
  cursor: pointer;
  padding: 6px;
  color: var(--text);
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 8px;
  transition: background-color 0.2s ease;
}

.filter-toggle-btn:hover {
  background-color: var(--hover-bg, rgba(0, 0, 0, 0.05));
}

.filter-content {
  display: block;
  margin-top: 14px;
  transition: all 0.3s ease;
}

.filter-content.collapsed {
  display: none;
}

/* PDF Loading Overlay */
.pdf-loading-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.7);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 9999;
}

.pdf-loading-spinner {
  background: var(--surface);
  border-radius: 16px;
  padding: 32px;
  text-align: center;
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.2);
  min-width: 200px;
}

.pdf-loading-spinner p {
  margin: 16px 0 0;
  color: var(--text);
  font-size: 14px;
}

.spinner {
  width: 40px;
  height: 40px;
  margin: 0 auto;
  border: 4px solid var(--border);
  border-top-color: var(--primary, #007bff);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  0% {
    transform: rotate(0deg);
  }
  100% {
    transform: rotate(360deg);
  }
}