@import url('https://fonts.googleapis.com/css2?family=Libre+Baskerville:ital,wght@0,400;0,700;1,400&family=Source+Serif+4:ital,opsz,wght@0,8..60,400;0,8..60,500;0,8..60,600;1,8..60,400&family=JetBrains+Mono:wght@400;500&display=swap');

:root {
  --color-bg: #faf8f5;
  --color-surface: #faf8f5;
  --color-text: #1c1917;
  --color-text-secondary: #57534e;
  --color-text-muted: #78716c;
  --color-accent: #9f1239;
  --color-accent-hover: #881337;
  --color-accent-light: #fdf2f8;
  --color-rule: #d6d3d1;
  --color-rule-heavy: #a8a29e;
  --font-display: 'Libre Baskerville', Georgia, serif;
  --font-body: 'Source Serif 4', 'Charter', Georgia, serif;
  --font-mono: 'JetBrains Mono', 'Consolas', monospace;
  --content-width: 820px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  padding: 0;
  font-family: var(--font-body);
  font-size: 17px;
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.7;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--color-accent);
  text-decoration-thickness: 1px;
  text-underline-offset: 2px;
}
a:hover {
  color: var(--color-accent-hover);
}

.site-header {
  padding: 2.5rem 2rem 1.8rem;
  max-width: var(--content-width);
  margin: 0 auto;
  width: 100%;
  border-bottom: 3px solid var(--color-text);
}

.site-title {
  font-family: var(--font-display);
  font-size: 1.65rem;
  font-weight: 700;
  margin: 0;
  color: var(--color-text);
  letter-spacing: -0.01em;
  line-height: 1.3;
}

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

main {
  flex: 1;
  max-width: var(--content-width);
  margin: 0 auto;
  padding: 2rem 2rem 3rem;
  width: 100%;
}

/* Banners */
.wip-warning {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  font-weight: 500;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: #92400e !important;
  background: #fef3c7 !important;
  border: 1px solid #d97706 !important;
  border-left: 4px solid #d97706 !important;
  border-radius: 0 !important;
  padding: 0.7rem 1.2rem !important;
  margin-bottom: 2rem;
}

.unverified-banner {
  font-size: 0.9rem;
  color: #1e3a5f;
  background: #eff6ff;
  border: 1px solid #93c5fd;
  border-left: 4px solid #3b82f6;
  padding: 0.8rem 1.2rem;
  margin-bottom: 2rem;
  line-height: 1.6;
}
.unverified-banner strong {
  font-weight: 600;
}
.unverified-banner a {
  color: #1d4ed8;
  font-weight: 600;
}

/* Problem list (home page) */
.problem-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.problem-card {
  padding: 1.2rem 0;
  border-bottom: 1px solid var(--color-rule);
}
.problem-card:first-child {
  padding-top: 0;
}
.problem-card:last-child {
  border-bottom: none;
}

.problem-card-link {
  text-decoration: none;
  color: var(--color-text);
  display: flex;
  align-items: baseline;
  gap: 0.75rem;
  width: 100%;
}

.problem-card-link:hover .problem-card-title {
  color: var(--color-accent);
}

.problem-card-id {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--color-text-muted);
  flex-shrink: 0;
  width: 1.8rem;
  text-align: right;
  padding-top: 0.2rem;
  align-self: flex-start;
}

.problem-card-body {
  flex: 1;
  min-width: 0;
}

.problem-card-title {
  font-family: var(--font-display);
  font-size: 1.05rem;
  font-weight: 700;
  margin: 0 0 0.25rem;
  line-height: 1.4;
  transition: color 0.15s;
}

.problem-card-meta {
  font-size: 0.8rem;
  color: var(--color-text-muted);
  line-height: 1.5;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0;
}
.problem-card-meta > span {
  display: inline;
}
.problem-card-meta > span + span::before {
  content: " · ";
  color: var(--color-rule-heavy);
  margin: 0 0.05rem;
}
.problem-card-meta a {
  color: var(--color-text-secondary);
  text-decoration: none;
}
.problem-card-meta a:hover {
  color: var(--color-accent);
  text-decoration: underline;
}

.area-pill {
  display: inline-flex;
  align-items: center;
  border: 1px solid #e7d7d7;
  background: #fff4f6;
  color: #881337;
  border-radius: 999px;
  padding: 0.05rem 0.5rem;
  font-family: var(--font-mono);
  font-size: 0.64rem;
  font-weight: 500;
  letter-spacing: 0.01em;
  margin-left: 0.4rem;
  vertical-align: middle;
  position: relative;
  top: -0.5px;
}

/* Pagination */
.pagination {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 0.25rem;
  margin: 2.5rem 0 1rem;
  flex-wrap: wrap;
}

.pagination a,
.pagination span {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  padding: 0.35rem 0.75rem;
  text-decoration: none;
  color: var(--color-text-secondary);
  border: 1px solid transparent;
}
.pagination a:hover {
  color: var(--color-accent);
  border-color: var(--color-rule);
}
.pagination .current {
  color: var(--color-accent);
  font-weight: 500;
  border-bottom: 2px solid var(--color-accent);
}
.pagination .disabled {
  opacity: 0.35;
  cursor: default;
  pointer-events: none;
}

/* Problem detail page */
.back-link {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  letter-spacing: 0.02em;
  color: var(--color-text-muted);
  text-decoration: none;
  margin-bottom: 1.5rem;
}
.back-link:hover {
  color: var(--color-accent);
}

.problem-header {
  margin-bottom: 2.5rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--color-rule);
}

.problem-topline {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  margin-bottom: 0.5rem;
}

.problem-number-badge {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--color-accent);
}
.problem-number-badge:empty {
  display: none;
}

.problem-id {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 500;
  color: var(--color-text-muted);
  letter-spacing: 0.03em;
}

.problem-title {
  font-family: var(--font-display);
  font-size: 1.55rem;
  font-weight: 700;
  line-height: 1.35;
  margin: 0 0 1rem;
}

.problem-source-block {
  margin-bottom: 1.2rem;
}

.problem-source-paper {
  font-size: 0.92rem;
  line-height: 1.5;
  color: var(--color-text-secondary);
}
.problem-source-paper a {
  color: var(--color-accent);
}

.problem-source-authors {
  font-size: 0.84rem;
  color: var(--color-text-muted);
  margin-top: 0.15rem;
  line-height: 1.5;
}

.problem-detail-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 0.2rem 1.8rem;
  padding-top: 1rem;
  border-top: 1px solid var(--color-rule);
  font-size: 0.84rem;
}

.problem-detail-item {
  display: flex;
  align-items: baseline;
  gap: 0.4rem;
}

.problem-detail-label {
  font-family: var(--font-mono);
  font-size: 0.66rem;
  font-weight: 500;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  white-space: nowrap;
}

.problem-detail-value {
  font-weight: 500;
  color: var(--color-text-secondary);
}

/* Sections */
.problem-section {
  margin: 2.5rem 0;
}

.problem-section h2 {
  font-family: var(--font-display);
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--color-text);
  margin: 0 0 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--color-accent);
  display: inline-block;
}

.problem-section p {
  margin: 0 0 1rem;
}

.section-note {
  margin: 0 0 0.8rem;
  color: var(--color-text-muted);
  font-size: 0.9rem;
  border-left: 2px solid var(--color-rule-heavy);
  padding-left: 0.6rem;
}

.problem-definition-box {
  border: 1px solid var(--color-rule-heavy);
  background: #f7f3ee;
  padding: 1rem 1.1rem;
  border-left: 4px solid var(--color-accent);
}

/* Buttons */
.copy-bibtex-btn,
.inline-action-btn {
  font-family: var(--font-mono);
  font-size: 0.76rem;
  margin: 0 0 1rem;
  padding: 0.35rem 0.65rem;
  border: 1px solid var(--color-rule);
  background: transparent;
  color: var(--color-text-secondary);
  cursor: pointer;
  letter-spacing: 0.01em;
}
.copy-bibtex-btn:hover,
.inline-action-btn:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.source-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-bottom: 0.75rem;
}

.raw-source-block {
  margin: 0 0 1rem;
  padding: 1rem;
  border: 1px solid var(--color-rule);
  background: #f5f0eb;
  white-space: pre-wrap;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.82rem;
  line-height: 1.6;
}

#problem-latex {
  overflow-x: auto;
  overflow-y: visible;
  width: 100%;
  padding: 0.5rem 0;
  white-space: pre-wrap;
}

#problem-latex .katex-display {
  margin: 1rem 0;
  overflow: visible;
  display: block;
}

.problem-section ul {
  margin: 0.5rem 0 1rem;
  padding-left: 1.5rem;
}

/* Literature review cards */
.lit-source-card {
  padding: 1.2rem 0;
  border-bottom: 1px solid var(--color-rule);
}
.lit-source-card:last-child {
  border-bottom: none;
}
.lit-source-heading {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  font-weight: 500;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 0.5rem;
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--color-rule);
  padding: 1.5rem 2rem;
  margin-top: auto;
}

.footer-content {
  max-width: var(--content-width);
  margin: 0 auto;
  font-size: 0.82rem;
  color: var(--color-text-muted);
  text-align: center;
}

.footer-maintainers {
  font-weight: 500;
  color: var(--color-text-secondary);
  margin-bottom: 0.15rem;
}

/* MathJax */
.katex {
  font-size: 1.05em;
}

@media (max-width: 640px) {
  .site-header {
    padding: 1.8rem 1.2rem 1.2rem;
  }
  .site-title {
    font-size: 1.3rem;
  }
  main {
    padding: 1.5rem 1.2rem 2rem;
  }
  .problem-card-link {
    gap: 0.5rem;
  }
  .problem-title {
    font-size: 1.3rem;
  }
  .problem-detail-grid {
    flex-direction: column;
    gap: 0.35rem;
  }
}