/* ========== Reset & Base ========== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg: #fafafa;
  --card-bg: #ffffff;
  --text: #1a1a2e;
  --text-muted: #555;
  --accent: #b31b1b;
  --accent-hover: #8b1515;
  --border: #e0e0e0;
  --code-bg: #f5f5f5;
  --cat-physics: #2e7d32;
  --cat-cs: #1565c0;
  --cat-math: #6a1b9a;
  --shadow: 0 1px 3px rgba(0,0,0,0.08);
  --radius: 6px;
  --max-width: 960px;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

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

/* ========== Header ========== */
header {
  background: var(--card-bg);
  border-bottom: 3px solid var(--accent);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: var(--shadow);
}

.header-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 12px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-size: 28px;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -1px;
}
.logo:hover { text-decoration: none; }
.logo-accent { color: var(--accent); }

nav { display: flex; gap: 24px; }
nav a {
  color: var(--text-muted);
  font-size: 15px;
  font-weight: 500;
  padding: 4px 0;
  border-bottom: 2px solid transparent;
  transition: all 0.2s;
}
nav a:hover, nav a.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
  text-decoration: none;
}

/* ========== Main ========== */
main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px 60px;
  width: 100%;
  flex: 1;
}

/* ========== Hero ========== */
.hero {
  text-align: center;
  padding: 40px 0 30px;
}
.hero h1 {
  font-size: 32px;
  font-weight: 700;
  margin-bottom: 8px;
}
.subtitle {
  color: var(--text-muted);
  font-size: 16px;
  margin-bottom: 24px;
}

.search-box {
  max-width: 600px;
  margin: 0 auto 16px;
}
.search-box input {
  width: 100%;
  padding: 12px 20px;
  font-size: 15px;
  border: 2px solid var(--border);
  border-radius: 30px;
  outline: none;
  transition: border-color 0.2s;
}
.search-box input:focus {
  border-color: var(--accent);
}

.stats {
  display: flex;
  gap: 24px;
  justify-content: center;
  color: var(--text-muted);
  font-size: 14px;
}

/* ========== Paper Cards ========== */
.paper-list { display: flex; flex-direction: column; gap: 16px; }

.paper-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow);
  transition: box-shadow 0.2s;
}
.paper-card:hover {
  box-shadow: 0 3px 12px rgba(0,0,0,0.12);
}

.paper-id {
  font-family: "SF Mono", "Consolas", "Menlo", monospace;
  font-size: 12px;
  color: var(--text-muted);
  margin-bottom: 6px;
}

.paper-title {
  font-size: 18px;
  font-weight: 600;
  line-height: 1.4;
  margin-bottom: 6px;
}
.paper-title a { color: var(--accent); }
.paper-title a:hover { text-decoration: underline; }

.paper-authors {
  font-size: 14px;
  color: var(--text-muted);
  margin-bottom: 8px;
}

.paper-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
  margin-bottom: 12px;
}

.category {
  display: inline-block;
  font-size: 12px;
  font-weight: 600;
  padding: 2px 10px;
  border-radius: 12px;
  color: white;
}
.cat-physics { background: var(--cat-physics); }
.cat-cs { background: var(--cat-cs); }
.cat-math { background: var(--cat-math); }

.date {
  font-size: 13px;
  color: var(--text-muted);
}

.paper-abstract {
  font-size: 14px;
  color: var(--text);
  line-height: 1.65;
  margin-bottom: 14px;
}

.paper-actions {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.btn {
  display: inline-block;
  font-size: 13px;
  font-weight: 600;
  padding: 6px 16px;
  border-radius: 4px;
  transition: all 0.2s;
  border: 1px solid;
}
.btn:hover { text-decoration: none; }

.btn-abstract {
  color: var(--accent);
  border-color: var(--accent);
  background: transparent;
}
.btn-abstract:hover {
  background: var(--accent);
  color: white;
}

.btn-pdf {
  color: white;
  background: var(--accent);
  border-color: var(--accent);
}
.btn-pdf:hover {
  background: var(--accent-hover);
  border-color: var(--accent-hover);
}

.btn-code {
  color: var(--cat-physics);
  border-color: var(--cat-physics);
  background: transparent;
}
.btn-code:hover {
  background: var(--cat-physics);
  color: white;
}

/* ========== Paper Detail Page (two-column with sidebar) ========== */
.paper-detail-wrapper {
  display: flex;
  gap: 24px;
  align-items: flex-start;
  margin-top: 30px;
}
.paper-detail {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 40px;
  box-shadow: var(--shadow);
  flex: 1;
  min-width: 0;
}
.paper-detail .paper-title {
  font-size: 24px;
  margin-bottom: 12px;
  color: var(--text);
}
.paper-detail .paper-authors {
  font-size: 16px;
  margin-bottom: 4px;
}
.paper-detail .affiliation {
  font-size: 14px;
  color: var(--text-muted);
  margin-bottom: 20px;
}
.paper-detail .abstract-label {
  font-size: 14px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--text-muted);
  margin-bottom: 8px;
}
.paper-detail .abstract-text {
  font-size: 15px;
  line-height: 1.75;
  margin-bottom: 24px;
  text-align: justify;
}
.paper-detail .keywords {
  font-size: 13px;
  color: var(--text-muted);
  margin-bottom: 24px;
}
.paper-detail .keywords strong {
  color: var(--text);
}

.detail-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 20px;
  padding: 16px 0;
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
  margin-bottom: 20px;
  font-size: 14px;
}
.detail-meta dt {
  font-weight: 600;
  color: var(--text-muted);
  font-size: 12px;
  text-transform: uppercase;
}
.detail-meta dd {
  margin-bottom: 8px;
}

.back-link {
  display: inline-block;
  margin-top: 20px;
  font-size: 14px;
}

/* ========== Access Paper Sidebar (arXiv-style) ========== */
.access-sidebar {
  width: 200px;
  flex-shrink: 0;
  position: sticky;
  top: 70px;
}
.access-panel {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 20px;
  box-shadow: var(--shadow);
}
.access-panel-label {
  font-size: 12px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-muted);
  margin-bottom: 14px;
  padding-bottom: 8px;
  border-bottom: 2px solid var(--accent);
}
.access-panel-links {
  display: flex;
  flex-direction: column;
  gap: 4px;
}
.access-panel-links a {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 14px;
  font-weight: 600;
  color: var(--accent);
  padding: 8px 8px;
  border-radius: 4px;
  transition: background 0.15s;
}
.access-panel-links a:hover {
  background: var(--code-bg);
  color: var(--accent-hover);
  text-decoration: none;
}
.access-panel-links .access-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border-radius: 4px;
  font-size: 11px;
  font-weight: 700;
  color: white;
  flex-shrink: 0;
}
.access-icon-pdf { background: var(--accent); }
.access-icon-html { background: #e65100; }
.access-icon-tex { background: #37474f; }
.access-panel-links .access-text {
  display: flex;
  flex-direction: column;
  line-height: 1.3;
}
.access-panel-links .access-text small {
  font-size: 11px;
  font-weight: 400;
  color: var(--text-muted);
}

/* Code link in sidebar */
.access-panel-extra {
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px solid var(--border);
}
.access-panel-extra a {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 13px;
  font-weight: 600;
  color: var(--cat-physics);
  padding: 6px 8px;
  border-radius: 4px;
  transition: background 0.15s;
}
.access-panel-extra a:hover {
  background: var(--code-bg);
  text-decoration: none;
}

/* Index card access links */
.paper-access {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
  margin-bottom: 12px;
  font-size: 13px;
}
.paper-access span.access-sep {
  color: var(--border);
}
.paper-access a {
  font-weight: 600;
}

/* ========== About / Submit Pages ========== */
.page-content {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 40px;
  margin-top: 30px;
  box-shadow: var(--shadow);
}
.page-content h1 {
  font-size: 28px;
  margin-bottom: 20px;
}
.page-content h2 {
  font-size: 20px;
  margin-top: 28px;
  margin-bottom: 12px;
  color: var(--accent);
}
.page-content p {
  margin-bottom: 14px;
  font-size: 15px;
  line-height: 1.7;
}
.page-content ul {
  margin: 0 0 14px 24px;
  font-size: 15px;
}
.page-content li {
  margin-bottom: 6px;
}

/* ========== Footer ========== */
footer {
  background: var(--card-bg);
  border-top: 1px solid var(--border);
  margin-top: auto;
}
.footer-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 20px;
  text-align: center;
  font-size: 13px;
  color: var(--text-muted);
}
.footer-inner p { margin-bottom: 4px; }

/* ========== Responsive ========== */
@media (max-width: 768px) {
  .paper-detail-wrapper {
    flex-direction: column;
  }
  .access-sidebar {
    width: 100%;
    position: static;
    order: -1;
  }
  .access-panel-links {
    flex-direction: row;
    gap: 8px;
  }
  .access-panel-links a {
    flex: 1;
    justify-content: center;
    padding: 10px 8px;
    background: var(--code-bg);
  }
}
@media (max-width: 640px) {
  .header-inner { flex-direction: column; gap: 8px; }
  .hero h1 { font-size: 24px; }
  .paper-detail { padding: 24px; }
  .paper-card { padding: 16px; }
  .detail-meta { flex-direction: column; gap: 12px; }
  .access-panel-links { flex-direction: column; }
  .access-panel-links a { justify-content: flex-start; }
}

/* ========== HTML Paper View ========== */
.paper-html-view {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 40px 48px;
  margin-top: 30px;
  box-shadow: var(--shadow);
  max-width: 800px;
  margin-left: auto;
  margin-right: auto;
}
.paper-html-view h1 { font-size: 24px; margin-bottom: 12px; line-height: 1.3; }
.paper-html-view h2 { font-size: 20px; margin-top: 32px; margin-bottom: 12px; color: var(--text); border-bottom: 1px solid var(--border); padding-bottom: 6px; }
.paper-html-view h3 { font-size: 17px; margin-top: 24px; margin-bottom: 8px; }
.paper-html-view p { font-size: 15px; line-height: 1.8; margin-bottom: 14px; text-align: justify; }
.paper-html-view .authors { font-size: 16px; color: var(--text-muted); margin-bottom: 4px; }
.paper-html-view .affiliation { font-size: 14px; color: var(--text-muted); margin-bottom: 20px; }
.paper-html-view .abstract-box { background: var(--code-bg); border-left: 4px solid var(--accent); padding: 16px 20px; margin: 20px 0; border-radius: 0 var(--radius) var(--radius) 0; }
.paper-html-view .abstract-box p { margin-bottom: 0; }
.paper-html-view .access-banner { display: flex; gap: 16px; align-items: center; padding: 12px 0; border-bottom: 1px solid var(--border); margin-bottom: 24px; font-size: 14px; flex-wrap: wrap; }
.paper-html-view .access-banner a { font-weight: 600; }
.paper-html-view .access-banner .current { color: var(--text); font-weight: 700; border-bottom: 2px solid var(--accent); padding-bottom: 2px; }
.paper-html-view .keywords { font-size: 13px; color: var(--text-muted); margin-top: 8px; }