/* ==========================================================================
   6G Latency Prediction — GitHub Pages Stylesheet
   ========================================================================== */

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

:root {
  --c-bg:        #ffffff;
  --c-bg-alt:    #f4f6fb;
  --c-surface:   #ffffff;
  --c-surface-2: #f0f2f7;
  --c-border:    #e2e6ef;
  --c-text:      #1e293b;
  --c-text-dim:  #475569;
  --c-text-mute: #94a3b8;
  --c-primary:   #4f46e5;
  --c-primary-d: #4338ca;
  --c-accent:    #7c3aed;
  --c-accent-2:  #8b5cf6;
  --c-green:     #059669;
  --c-yellow:    #d97706;
  --c-red:       #dc2626;
  --c-grad-1:    linear-gradient(135deg, #4f46e5, #7c3aed);
  --c-grad-2:    linear-gradient(135deg, #7c3aed, #a855f7);
  --font:        'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono:   'JetBrains Mono', 'Fira Code', monospace;
  --max-w:       1200px;
  --radius:      12px;
  --radius-sm:   8px;
  --shadow:      0 4px 24px rgba(0,0,0,0.06);
  --shadow-lg:   0 8px 48px rgba(0,0,0,0.08);
  --transition:  0.3s cubic-bezier(.4,0,.2,1);
}

html { scroll-behavior: smooth; font-size: 16px; }
body {
  font-family: var(--font);
  background: var(--c-bg);
  color: var(--c-text);
  line-height: 1.7;
  overflow-x: hidden;
}

a { color: var(--c-primary); text-decoration: none; transition: color var(--transition); }
a:hover { color: var(--c-accent); }
code {
  font-family: var(--font-mono);
  background: var(--c-surface-2);
  padding: 0.15em 0.45em;
  border-radius: 4px;
  font-size: 0.88em;
  color: var(--c-primary);
}

.container { max-width: var(--max-w); margin: 0 auto; padding: 0 1.5rem; }

/* ── Navbar ──────────────────────────────────────────────────────────────── */
#navbar {
  position: fixed; top: 0; left: 0; width: 100%; z-index: 1000;
  background: rgba(255,255,255,0.85);
  backdrop-filter: blur(20px);
  border-bottom: 1px solid transparent;
  transition: all var(--transition);
}
#navbar.scrolled {
  background: rgba(255,255,255,0.95);
  border-bottom-color: var(--c-border);
  box-shadow: 0 2px 20px rgba(0,0,0,0.06);
}
.nav-container {
  max-width: var(--max-w); margin: 0 auto; padding: 0 1.5rem;
  display: flex; align-items: center; justify-content: space-between; height: 64px;
}
.nav-logo {
  font-weight: 700; font-size: 1.1rem; color: var(--c-text);
  letter-spacing: -0.02em;
}
.nav-logo:hover { color: var(--c-primary); }
.nav-links {
  list-style: none; display: flex; align-items: center; gap: 0.2rem;
}
.nav-links a {
  display: block; padding: 0.4rem 0.7rem; border-radius: var(--radius-sm);
  font-size: 0.85rem; font-weight: 500; color: var(--c-text-dim);
  transition: all var(--transition);
}
.nav-links a:hover, .nav-links a.active {
  color: var(--c-text); background: var(--c-surface);
}
.btn-nav {
  background: var(--c-grad-1) !important; color: #fff !important;
  padding: 0.4rem 1rem !important; border-radius: 20px !important;
  font-weight: 600 !important;
}
.btn-nav:hover { opacity: 0.9; }
.nav-toggle { display: none; background: none; border: none; cursor: pointer; padding: 6px; }
.nav-toggle span {
  display: block; width: 22px; height: 2px; background: var(--c-text); margin: 5px 0;
  border-radius: 2px; transition: var(--transition);
}

/* ── Hero ────────────────────────────────────────────────────────────────── */
#hero {
  position: relative; min-height: 100vh;
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  text-align: center; padding: 6rem 1.5rem 3rem;
  overflow: hidden;
}
.hero-bg {
  position: absolute; inset: 0;
  background:
    radial-gradient(ellipse 80% 60% at 50% 10%, rgba(79,70,229,0.08), transparent),
    radial-gradient(ellipse 60% 50% at 80% 50%, rgba(124,58,237,0.06), transparent),
    radial-gradient(ellipse 60% 50% at 20% 80%, rgba(168,85,247,0.05), transparent);
}
.hero-content { position: relative; z-index: 1; max-width: 900px; }
.hero-tag {
  display: inline-block; padding: 0.35rem 1rem; border-radius: 20px;
  background: var(--c-surface); border: 1px solid var(--c-border);
  font-size: 0.82rem; font-weight: 500; color: var(--c-primary);
  letter-spacing: 0.04em; text-transform: uppercase; margin-bottom: 1.5rem;
}
#hero h1 {
  font-size: clamp(2.2rem, 5vw, 3.8rem); font-weight: 800;
  line-height: 1.15; letter-spacing: -0.03em; margin-bottom: 1.5rem;
}
.gradient-text {
  background: var(--c-grad-1); -webkit-background-clip: text;
  -webkit-text-fill-color: transparent; background-clip: text;
}
.hero-sub {
  font-size: 1.1rem; color: var(--c-text-dim); max-width: 700px; margin: 0 auto 2rem;
  line-height: 1.8;
}
.hero-buttons { display: flex; gap: 1rem; justify-content: center; flex-wrap: wrap; margin-bottom: 3rem; }
.btn {
  display: inline-flex; align-items: center; gap: 0.5rem;
  padding: 0.75rem 1.8rem; border-radius: 10px;
  font-weight: 600; font-size: 0.95rem;
  transition: all var(--transition); cursor: pointer; border: none;
}
.btn-primary {
  background: var(--c-grad-1); color: #fff;
  box-shadow: 0 4px 20px rgba(79,70,229,0.25);
}
.btn-primary:hover { transform: translateY(-2px); box-shadow: 0 6px 30px rgba(79,70,229,0.35); color: #fff; }
.btn-outline {
  background: transparent; color: var(--c-text);
  border: 1px solid var(--c-border); backdrop-filter: blur(8px);
}
.btn-outline:hover { border-color: var(--c-primary); color: var(--c-primary); transform: translateY(-2px); }
.btn-outline svg { flex-shrink: 0; }

.hero-stats {
  display: flex; gap: 2.5rem; justify-content: center; flex-wrap: wrap;
}
.stat { display: flex; flex-direction: column; align-items: center; }
.stat-num {
  font-size: 1.8rem; font-weight: 700;
  background: var(--c-grad-1); -webkit-background-clip: text;
  -webkit-text-fill-color: transparent; background-clip: text;
}
.stat-label { font-size: 0.8rem; color: var(--c-text-mute); text-transform: uppercase; letter-spacing: 0.06em; }

.scroll-indicator {
  position: absolute; bottom: 2rem; display: flex; flex-direction: column; align-items: center; gap: 0.5rem;
  color: var(--c-text-mute); font-size: 0.75rem;
  animation: fadeInUp 1s ease 1s both;
}
.scroll-arrow {
  width: 20px; height: 20px; border-right: 2px solid var(--c-text-mute);
  border-bottom: 2px solid var(--c-text-mute); transform: rotate(45deg);
  animation: bounce 2s ease infinite;
}
@keyframes bounce {
  0%, 60%, 100% { transform: rotate(45deg) translateY(0); }
  30% { transform: rotate(45deg) translateY(6px); }
}
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ── Sections ────────────────────────────────────────────────────────────── */
section { padding: 5rem 0; }
.alt-bg { background: var(--c-bg-alt); }

.section-title {
  font-size: clamp(1.8rem, 3vw, 2.4rem); font-weight: 700;
  letter-spacing: -0.02em; margin-bottom: 0.8rem; text-align: center;
}
.section-subtitle {
  text-align: center; color: var(--c-text-dim); max-width: 750px;
  margin: 0 auto 3rem; font-size: 1.05rem; line-height: 1.8;
}

/* ── Cards ────────────────────────────────────────────────────────────────── */
.cards-grid {
  display: grid; gap: 1.5rem;
}
.cards-grid.two { grid-template-columns: repeat(2, 1fr); }
.cards-grid.three { grid-template-columns: repeat(3, 1fr); }

.card {
  background: var(--c-surface); border: 1px solid var(--c-border);
  border-radius: var(--radius); padding: 1.8rem;
  transition: all var(--transition);
  box-shadow: 0 1px 4px rgba(0,0,0,0.04);
}
.card:hover {
  border-color: var(--c-primary); transform: translateY(-3px);
  box-shadow: 0 8px 32px rgba(79,70,229,0.1);
}
.card h3 { font-size: 1.15rem; margin-bottom: 0.6rem; }
.card p, .card li { color: var(--c-text-dim); font-size: 0.92rem; }
.card ul { padding-left: 1.2rem; }
.card ul li { margin-bottom: 0.3rem; }
.card-icon { font-size: 2rem; margin-bottom: 0.8rem; }
.card.mini { padding: 1.2rem; }
.card.mini h4 { font-size: 1rem; margin-bottom: 0.4rem; color: var(--c-primary); }
.card.mini p { font-size: 0.88rem; }

/* ── Tables ───────────────────────────────────────────────────────────────── */
.table-wrapper { overflow-x: auto; }
table {
  width: 100%; border-collapse: collapse; font-size: 0.9rem;
}
thead { background: var(--c-bg-alt); }
th, td {
  padding: 0.75rem 1rem; text-align: left;
  border-bottom: 1px solid var(--c-border);
}
th { font-weight: 600; color: var(--c-text); font-size: 0.85rem; text-transform: uppercase; letter-spacing: 0.04em; }
td { color: var(--c-text-dim); }
tr:hover td { background: rgba(79,70,229,0.03); }
.highlight-row td { background: rgba(79,70,229,0.06); color: var(--c-text); }

/* ── Objectives box ──────────────────────────────────────────────────────── */
.objectives-box {
  margin-top: 2.5rem; padding: 2rem;
  background: var(--c-surface); border: 1px solid var(--c-border);
  border-left: 4px solid var(--c-primary); border-radius: var(--radius);
}
.objectives-box h3 { margin-bottom: 1rem; color: var(--c-primary); }
.objectives-box li { margin-bottom: 0.5rem; color: var(--c-text-dim); }
.objectives-box ul { padding-left: 1.5rem; }

/* ── Pipeline flow ───────────────────────────────────────────────────────── */
.pipeline-flow {
  display: flex; align-items: flex-start; gap: 0.5rem;
  overflow-x: auto; padding: 1.5rem 0 2rem;
  margin-bottom: 2rem;
}
.pipeline-step {
  flex: 1; min-width: 160px; padding: 1.5rem 1rem;
  background: var(--c-surface); border: 1px solid var(--c-border);
  border-radius: var(--radius); text-align: center;
  transition: all var(--transition);
}
.pipeline-step:hover {
  border-color: var(--c-primary);
  box-shadow: 0 4px 20px rgba(79,70,229,0.1);
}
.step-number {
  display: inline-flex; align-items: center; justify-content: center;
  width: 32px; height: 32px; border-radius: 50%;
  background: var(--c-grad-1); color: #fff;
  font-weight: 700; font-size: 0.85rem; margin-bottom: 0.8rem;
}
.pipeline-step h4 { font-size: 0.95rem; margin-bottom: 0.4rem; }
.pipeline-step p { font-size: 0.8rem; color: var(--c-text-dim); }
.pipeline-arrow {
  display: flex; align-items: center; color: var(--c-text-mute);
  font-size: 1.5rem; padding-top: 2rem; flex-shrink: 0;
}

.feature-groups { margin-top: 2rem; }
.feature-groups h3 { text-align: center; margin-bottom: 1.5rem; }

/* ── Model tiers ─────────────────────────────────────────────────────────── */
.tier { margin-bottom: 3rem; }
.tier-label {
  font-size: 1.2rem; font-weight: 600; margin-bottom: 1.2rem;
  padding-bottom: 0.5rem; border-bottom: 2px solid var(--c-border);
}
.model-card { position: relative; }
.model-badge {
  position: absolute; top: 1rem; right: 1rem;
  padding: 0.2rem 0.7rem; border-radius: 12px;
  font-size: 0.7rem; font-weight: 600; text-transform: uppercase; letter-spacing: 0.04em;
}
.model-badge.baseline { background: var(--c-surface-2); color: var(--c-text-mute); border: 1px solid var(--c-border); }
.model-badge.advanced { background: rgba(79,70,229,0.1); color: var(--c-primary); border: 1px solid rgba(79,70,229,0.2); }
.model-card h4 { padding-right: 5rem; }

/* ── Ensemble diagram ────────────────────────────────────────────────────── */
.ensemble-diagram {
  display: flex; flex-direction: column; align-items: center; gap: 0.5rem;
  padding: 2rem;
  background: var(--c-bg-alt); border: 1px solid var(--c-border); border-radius: var(--radius);
}
.ens-level {
  display: flex; align-items: center; gap: 1rem; flex-wrap: wrap; justify-content: center;
}
.ens-tag {
  font-weight: 600; font-size: 0.85rem; color: var(--c-text-mute);
  text-transform: uppercase; letter-spacing: 0.04em; min-width: 80px;
}
.ens-models { display: flex; gap: 0.8rem; flex-wrap: wrap; justify-content: center; }
.ens-chip {
  padding: 0.5rem 1.2rem; border-radius: 8px;
  background: var(--c-surface-2); border: 1px solid var(--c-border);
  font-size: 0.88rem; font-weight: 500;
}
.ens-chip.meta-chip {
  background: rgba(79,70,229,0.08); border-color: rgba(79,70,229,0.2); color: var(--c-primary);
}
.ens-arrow { font-size: 1.5rem; color: var(--c-text-mute); }
.ens-level.meta .ens-tag { color: var(--c-primary); }

/* ── Results ─────────────────────────────────────────────────────────────── */
.results-tables { display: grid; gap: 2rem; }
.result-block h3 { margin-bottom: 1rem; font-size: 1.1rem; }
.callout {
  padding: 1.2rem 1.5rem; border-radius: var(--radius-sm);
  background: rgba(79,70,229,0.04); border: 1px solid rgba(79,70,229,0.15);
  font-size: 0.92rem; color: var(--c-text-dim);
  line-height: 1.7;
}

/* ── SHAP feature bars ───────────────────────────────────────────────────── */
.shap-features { margin-top: 2.5rem; }
.shap-features h3 { margin-bottom: 1.2rem; text-align: center; }
.feature-bar-chart { max-width: 700px; margin: 0 auto; }
.feature-bar {
  display: flex; align-items: center; gap: 1rem; margin-bottom: 0.6rem;
}
.fb-label {
  min-width: 180px; text-align: right; font-size: 0.85rem;
  font-family: var(--font-mono); color: var(--c-text-dim);
}
.fb-track {
  flex: 1; height: 22px; background: var(--c-surface-2);
  border-radius: 4px; overflow: hidden;
}
.fb-fill {
  height: 100%; border-radius: 4px;
  background: var(--c-grad-1);
  transition: width 1s ease;
}

/* ── Methods row (enforcement) ───────────────────────────────────────────── */
.methods-row {
  display: grid; grid-template-columns: repeat(3,1fr); gap: 1.5rem;
}
.method-box {
  padding: 1.5rem; border-radius: var(--radius);
  background: var(--c-surface); border: 1px solid var(--c-border);
  text-align: center;
}
.method-box h4 { color: var(--c-primary); margin-bottom: 0.5rem; }
.method-box p { font-size: 0.88rem; color: var(--c-text-dim); }

/* ── Recommendations ─────────────────────────────────────────────────────── */
.rec-cards { display: flex; flex-direction: column; gap: 1.5rem; max-width: 800px; margin: 0 auto; }
.rec-card {
  display: flex; gap: 1.5rem; align-items: flex-start;
  padding: 1.8rem; background: var(--c-surface);
  border: 1px solid var(--c-border); border-radius: var(--radius);
  transition: all var(--transition);
}
.rec-card:hover { border-color: var(--c-primary); transform: translateX(4px); }
.rec-number {
  flex-shrink: 0; width: 48px; height: 48px;
  display: flex; align-items: center; justify-content: center;
  border-radius: 12px; background: var(--c-grad-1);
  color: #fff; font-weight: 800; font-size: 1.1rem;
}
.rec-content h4 { margin-bottom: 0.4rem; }
.rec-content p { font-size: 0.9rem; color: var(--c-text-dim); }

/* ── Environment table ───────────────────────────────────────────────────── */
.env-table { display: flex; flex-direction: column; gap: 0.3rem; margin-top: 0.5rem; }
.env-row {
  display: flex; justify-content: space-between; padding: 0.4rem 0;
  border-bottom: 1px solid var(--c-border); font-size: 0.88rem;
}
.env-row span:first-child { font-weight: 500; }
.env-row span:last-child { font-family: var(--font-mono); color: var(--c-primary); font-size: 0.85rem; }

/* ── Code blocks ─────────────────────────────────────────────────────────── */
pre {
  background: var(--c-surface-2); border: 1px solid var(--c-border);
  border-radius: var(--radius-sm); padding: 1.2rem 1.5rem;
  overflow-x: auto; font-size: 0.82rem; line-height: 1.8;
}
pre code {
  background: none; padding: 0; color: var(--c-text-dim); font-size: inherit;
}
.tree { font-size: 0.82rem; max-width: 700px; margin: 0 auto; }

/* ── Contributors ────────────────────────────────────────────────────────── */
.contributors-grid {
  display: flex; gap: 2rem; justify-content: center; flex-wrap: wrap;
}
.contributor-card {
  display: flex; flex-direction: column; align-items: center; gap: 1rem;
  padding: 2.5rem 3rem; background: var(--c-surface);
  border: 1px solid var(--c-border); border-radius: var(--radius);
  transition: all var(--transition);
}
.contributor-card:hover {
  border-color: var(--c-primary); transform: translateY(-4px);
  box-shadow: 0 12px 40px rgba(79,70,229,0.1);
}
.avatar {
  width: 96px; height: 96px; border-radius: 50%; overflow: hidden;
  border: 3px solid var(--c-border);
  transition: border-color var(--transition);
}
.contributor-card:hover .avatar { border-color: var(--c-primary); }
.avatar img { width: 100%; height: 100%; object-fit: cover; }
.avatar-fallback {
  width: 100%; height: 100%;
  display: flex; align-items: center; justify-content: center;
  background: var(--c-grad-1); color: #fff;
  font-size: 1.6rem; font-weight: 700;
}
.contributor-card h3 { font-size: 1.2rem; }
.contributor-link {
  display: inline-flex; align-items: center; gap: 0.4rem;
  font-size: 0.9rem; color: var(--c-text-mute);
}
.contributor-link:hover { color: var(--c-primary); }

/* ── Footer ──────────────────────────────────────────────────────────────── */
footer {
  padding: 3rem 0 2rem;
  background: var(--c-bg-alt); border-top: 1px solid var(--c-border);
}
.footer-content {
  display: flex; justify-content: space-between; align-items: center;
  margin-bottom: 1.5rem;
}
.footer-left h3 { font-size: 1.1rem; margin-bottom: 0.3rem; }
.footer-left p { font-size: 0.85rem; color: var(--c-text-mute); }
.footer-right a { color: var(--c-text-mute); transition: color var(--transition); }
.footer-right a:hover { color: var(--c-primary); }
.footer-bottom { text-align: center; padding-top: 1.5rem; border-top: 1px solid var(--c-border); }
.footer-bottom p { font-size: 0.8rem; color: var(--c-text-mute); }

/* ── Responsive ──────────────────────────────────────────────────────────── */
@media (max-width: 900px) {
  .cards-grid.three { grid-template-columns: repeat(2, 1fr); }
  .methods-row { grid-template-columns: 1fr; }
  .pipeline-flow { flex-direction: column; align-items: center; }
  .pipeline-arrow { transform: rotate(90deg); padding: 0; }
}

@media (max-width: 640px) {
  .cards-grid.two, .cards-grid.three { grid-template-columns: 1fr; }
  .hero-stats { gap: 1.5rem; }
  .stat-num { font-size: 1.4rem; }
  .nav-links {
    display: none; position: fixed; top: 64px; left: 0; right: 0;
    background: rgba(255,255,255,0.98); backdrop-filter: blur(20px);
    flex-direction: column; padding: 1rem; gap: 0;
    border-bottom: 1px solid var(--c-border);
  }
  .nav-links.open { display: flex; }
  .nav-links a { padding: 0.8rem 1rem; }
  .nav-toggle { display: block; }
  .rec-card { flex-direction: column; align-items: center; text-align: center; }
  .fb-label { min-width: 130px; font-size: 0.75rem; }
  .contributor-card { padding: 1.8rem 2rem; }
  .footer-content { flex-direction: column; gap: 1rem; text-align: center; }
}