/* --- Design tokens --- */
:root {
  --color-bg: #f6f5f2;
  --color-surface: #ffffff;
  --color-surface-hover: #fafaf9;
  --color-text: #1f1e1b;
  --color-text-muted: #5c5a56;
  --color-accent: #0d6b4c;
  --color-accent-hover: #0a5840;
  --color-border: #e5e3df;
  --color-border-focus: #0d6b4c;
  --font-sans: 'Figtree', system-ui, -apple-system, sans-serif;
  --radius-sm: 8px;
  --radius-md: 10px;
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.06);
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 2.5rem;
}

* {
  box-sizing: border-box;
}

body {
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.6;
  color: var(--color-text);
  background: var(--color-bg);
  margin: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* --- Layout --- */
body > .site-header {
  flex-shrink: 0;
}

body > main {
  flex: 1;
  width: 100%;
  max-width: 52rem;
  margin: 0 auto;
  padding: var(--space-lg) var(--space-md);
}

body > .footer {
  flex-shrink: 0;
}

/* --- Header --- */
.site-header {
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  padding: var(--space-xl) var(--space-md);
  text-align: center;
}

.site-header h1 {
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin: 0 0 var(--space-sm) 0;
  color: var(--color-text);
}

.tagline {
  margin: 0;
  font-size: 0.9375rem;
  color: var(--color-text-muted);
  font-weight: 400;
}

.tagline a {
  color: var(--color-accent);
  text-decoration: none;
  font-weight: 500;
}

.tagline a:hover {
  text-decoration: underline;
  color: var(--color-accent-hover);
}

/* --- Filters panel --- */
.filters {
  background: var(--color-surface);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--color-border);
  padding: var(--space-lg);
  margin-bottom: var(--space-xl);
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-md);
  align-items: flex-end;
}

.filters label {
  display: flex;
  flex-direction: column;
  gap: var(--space-xs);
  min-width: 0;
}

.filters label span {
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.filters select {
  min-width: 11rem;
  padding: 0.625rem 2rem 0.625rem 0.75rem;
  font-family: var(--font-sans);
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--color-text);
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%235c5a56' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='m6 9 6 6 6-6'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.6rem center;
}

.filters select:hover:not(:disabled) {
  border-color: var(--color-text-muted);
}

.filters select:focus {
  outline: none;
  border-color: var(--color-border-focus);
  box-shadow: 0 0 0 3px rgba(13, 107, 76, 0.15);
}

.filters select:disabled {
  background-color: #ecebe8;
  color: var(--color-text-muted);
  cursor: not-allowed;
  opacity: 0.85;
}

/* --- Results --- */
.results {
  min-height: 3rem;
}

.results-loading {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  color: var(--color-text-muted);
  font-size: 0.9375rem;
}

.results-loading.hidden {
  display: none !important;
}

.spinner {
  width: 1.25rem;
  height: 1.25rem;
  border: 2px solid var(--color-border);
  border-top-color: var(--color-accent);
  border-radius: 50%;
  animation: spin 0.7s linear infinite;
}

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

.results-empty {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--space-xl);
  text-align: center;
}

.results-empty p {
  margin: 0;
  color: var(--color-text-muted);
  font-size: 1rem;
}

.results-empty code {
  font-size: 0.875em;
  background: var(--color-bg);
  padding: 0.15em 0.4em;
  border-radius: 4px;
  font-family: var(--font-sans);
}

.results-list {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  padding: var(--space-lg);
}

.results-title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin: 0 0 var(--space-md) 0;
  padding-bottom: var(--space-sm);
  border-bottom: 1px solid var(--color-border);
}

.papers-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.papers-list li {
  margin: 0;
  border-bottom: 1px solid var(--color-border);
}

.papers-list li:last-child {
  border-bottom: none;
}

.papers-list a {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding: 0.75rem 0;
  color: var(--color-accent);
  text-decoration: none;
  font-weight: 500;
  font-size: 0.9375rem;
  transition: background 0.15s ease, color 0.15s ease;
}

.papers-list a:hover {
  color: var(--color-accent-hover);
  background: var(--color-surface-hover);
  padding-left: var(--space-sm);
  padding-right: var(--space-sm);
  margin-left: calc(-1 * var(--space-sm));
  margin-right: calc(-1 * var(--space-sm));
  border-radius: var(--radius-sm);
}

.papers-list a::before {
  content: '';
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--color-accent);
  flex-shrink: 0;
}

.hidden {
  display: none !important;
}

/* --- Footer --- */
.footer {
  margin-top: auto;
  padding: var(--space-lg) var(--space-md);
  border-top: 1px solid var(--color-border);
  background: var(--color-surface);
  font-size: 0.875rem;
  color: var(--color-text-muted);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-lg);
}

.footer a {
  color: var(--color-accent);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-weight: 500;
  transition: color 0.15s ease;
}

.footer a:hover {
  color: var(--color-accent-hover);
  text-decoration: none;
}

.footer-icon {
  width: 1.2rem;
  height: 1.2rem;
  flex-shrink: 0;
}

/* --- Responsive --- */
@media (max-width: 640px) {
  .site-header {
    padding: var(--space-lg) var(--space-md);
  }

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

  .filters {
    flex-direction: column;
    align-items: stretch;
  }

  .filters label {
    width: 100%;
  }

  .filters select {
    min-width: 0;
    width: 100%;
  }

  .results-list,
  .results-empty {
    padding: var(--space-md);
  }
}