/* ==========================================================================
   SPARK Blog — inspired by Med-AI-Scientist Homepage style
   ========================================================================== */

:root {
  --c-bg: #ffffff;
  --c-bg-soft: #f7f8fb;
  --c-bg-softer: #fbfcfe;
  --c-border: #e5e7eb;
  --c-border-soft: #eef0f4;
  --c-text: #0f172a;
  --c-text-muted: #475569;
  --c-text-soft: #64748b;
  --c-primary: #1a56db;
  --c-primary-soft: #e7efff;
  --c-primary-deep: #123a9d;
  --c-accent: #f59e0b;
  --c-accent-soft: #fff7e6;
  --c-danger: #dc2626;
  --c-success: #15803d;
  --c-ok-soft: #ecfdf5;
  --c-shadow: 0 1px 2px rgba(15,23,42,0.04), 0 4px 12px rgba(15,23,42,0.05);
  --c-shadow-lg: 0 8px 24px rgba(15,23,42,0.08);
  --radius-sm: 6px;
  --radius: 10px;
  --radius-lg: 16px;
  --container: 1120px;
  --nav-h: 62px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: calc(var(--nav-h) + 12px); }
body {
  margin: 0;
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC", "Microsoft YaHei", sans-serif;
  color: var(--c-text);
  background: var(--c-bg);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}
img { max-width: 100%; height: auto; display: block; }
a { color: var(--c-primary); text-decoration: none; }
a:hover { text-decoration: underline; }

.container { max-width: var(--container); margin: 0 auto; padding: 0 24px; }

/* ----- Top nav ----- */
.site-nav {
  position: sticky; top: 0; z-index: 50;
  height: var(--nav-h);
  background: rgba(255,255,255,0.92);
  backdrop-filter: saturate(180%) blur(10px);
  -webkit-backdrop-filter: saturate(180%) blur(10px);
  border-bottom: 1px solid var(--c-border-soft);
}
.site-nav .wrap {
  max-width: var(--container);
  margin: 0 auto; padding: 0 24px;
  height: 100%;
  display: flex; align-items: center; justify-content: space-between;
  gap: 16px;
}
.brand { display: flex; align-items: center; gap: 10px; font-weight: 700; letter-spacing: 0.02em; }
.brand-logo {
  width: 28px; height: 28px; border-radius: 8px;
  background: linear-gradient(135deg, var(--c-primary), #4f7cff);
  display: inline-grid; place-items: center; color: #fff; font-size: 14px; font-weight: 800;
  box-shadow: var(--c-shadow);
}
.brand-name { color: var(--c-text); }
.nav-links { display: flex; align-items: center; gap: 4px; flex-wrap: wrap; }
.nav-links a {
  color: var(--c-text-muted); font-weight: 500;
  padding: 8px 12px; border-radius: 8px; font-size: 14px;
  text-decoration: none;
}
.nav-links a:hover { background: var(--c-bg-soft); color: var(--c-text); }
.nav-cta {
  margin-left: 8px; display: inline-flex; align-items: center; gap: 6px;
  background: var(--c-primary); color: #fff !important;
  padding: 8px 14px !important; border-radius: 999px !important; font-weight: 600 !important;
}
.nav-cta:hover { background: var(--c-primary-deep); text-decoration: none; }

/* ----- Hugging Face accents ----- */
.nav-hf {
  display: inline-flex; align-items: center; gap: 6px;
  background: #FFD21E; color: #1f1300 !important;
  padding: 6px 12px !important; border-radius: 999px !important;
  font-weight: 700 !important; font-size: 13px;
  border: 1px solid #f0c400;
  transition: transform .15s ease, box-shadow .2s ease;
}
.nav-hf:hover { background: #FFCE00; text-decoration: none; transform: translateY(-1px); box-shadow: var(--c-shadow); }
.nav-hf .hf-logo { width: 18px; height: 18px; display: inline-block; }

.btn.hf {
  background: #FFD21E; color: #1f1300 !important;
  border-color: #f0c400;
}
.btn.hf:hover { background: #FFCE00; border-color: #e7ba00; }
.btn .hf-logo { width: 20px; height: 20px; display: inline-block; }

.hf-card {
  border-color: #f7e8a6;
  background: linear-gradient(180deg, #fffbea 0%, #ffffff 90%);
}
.hf-card:hover { border-color: #f0c400; }
.hf-card h3 { display: inline-flex; align-items: center; gap: 8px; }
.hf-card .hf-logo { width: 24px; height: 24px; display: inline-block; vertical-align: middle; }

.nav-toggle {
  display: none;
  background: none; border: 1px solid var(--c-border); border-radius: 8px;
  width: 38px; height: 38px; cursor: pointer;
  align-items: center; justify-content: center;
}

/* ----- Hero ----- */
.hero {
  position: relative;
  padding: 72px 0 48px;
  background:
    radial-gradient(900px 480px at 80% -120px, rgba(26,86,219,0.10), transparent 60%),
    radial-gradient(700px 500px at 8% 20%, rgba(245,158,11,0.08), transparent 60%),
    linear-gradient(180deg, #fbfcfe 0%, #ffffff 100%);
  border-bottom: 1px solid var(--c-border-soft);
}
.hero .eyebrow {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 6px 12px; border-radius: 999px;
  background: var(--c-primary-soft); color: var(--c-primary-deep);
  font-size: 12.5px; font-weight: 600; letter-spacing: 0.04em;
  text-transform: uppercase;
}
.hero h1 {
  margin: 18px 0 10px;
  font-size: clamp(34px, 5vw, 56px);
  line-height: 1.08; font-weight: 800; letter-spacing: -0.02em;
}
.hero h1 .gradient {
  background: linear-gradient(90deg, #1a56db, #7c3aed 60%, #f59e0b);
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.hero .tagline {
  color: var(--c-text-muted);
  font-size: clamp(16px, 1.6vw, 19px);
  max-width: 880px;
  margin: 0 0 18px;
}
.hero .bullets {
  display: flex; flex-wrap: wrap; gap: 10px; margin: 18px 0 22px;
}
.hero .bullets .chip {
  background: #fff; border: 1px solid var(--c-border);
  border-radius: 999px; padding: 7px 14px; font-size: 13.5px; color: var(--c-text-muted);
  display: inline-flex; align-items: center; gap: 8px;
}
.hero .bullets .chip b { color: var(--c-text); font-weight: 700; }
.hero .bullets .chip .dot { width: 7px; height: 7px; border-radius: 50%; background: var(--c-primary); display: inline-block; }
.hero .bullets .chip.warm .dot { background: var(--c-accent); }
.hero .bullets .chip.green .dot { background: var(--c-success); }

.hero .ctas { display: flex; flex-wrap: wrap; gap: 10px; }
.btn {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 11px 18px; border-radius: 999px; font-weight: 600;
  border: 1px solid var(--c-border); background: #fff; color: var(--c-text) !important;
  box-shadow: var(--c-shadow);
  transition: transform .15s ease, box-shadow .2s ease;
  text-decoration: none;
}
.btn:hover { transform: translateY(-1px); box-shadow: var(--c-shadow-lg); text-decoration: none; }
.btn.primary { background: var(--c-primary); color: #fff !important; border-color: var(--c-primary); }
.btn.primary:hover { background: var(--c-primary-deep); border-color: var(--c-primary-deep); }
.btn.ghost { background: #fff; }
.btn svg { width: 16px; height: 16px; }

.hero .institutions {
  margin-top: 30px;
  display: flex; flex-wrap: wrap; gap: 10px; align-items: center;
}
.inst-chip {
  padding: 8px 14px; border: 1px dashed var(--c-border); border-radius: 10px;
  background: #fff; color: var(--c-text-muted); font-size: 13.5px;
}

/* ----- Sections ----- */
.section { padding: 72px 0; }
.section.alt { background: var(--c-bg-soft); border-top: 1px solid var(--c-border-soft); border-bottom: 1px solid var(--c-border-soft); }
.section-eyebrow {
  text-transform: uppercase; font-size: 12px; letter-spacing: 0.12em;
  color: var(--c-primary); font-weight: 700;
}
.section h2 {
  margin: 6px 0 10px; font-size: clamp(26px, 3vw, 36px);
  font-weight: 800; letter-spacing: -0.015em;
}
.section .lead {
  color: var(--c-text-muted); font-size: 17px; max-width: 880px; margin: 0 0 28px;
}

/* ----- Cards ----- */
.card {
  background: #fff; border: 1px solid var(--c-border-soft);
  border-radius: var(--radius-lg); padding: 22px;
  box-shadow: var(--c-shadow);
  transition: transform .15s ease, box-shadow .2s ease, border-color .2s ease;
}
.card:hover { transform: translateY(-2px); box-shadow: var(--c-shadow-lg); border-color: #dbe3f5; }
.card h3 { margin: 0 0 8px; font-size: 18px; letter-spacing: -0.01em; }
.card p { color: var(--c-text-muted); margin: 0; font-size: 15px; }

.grid { display: grid; gap: 18px; }
.grid.cols-3 { grid-template-columns: repeat(3, minmax(0,1fr)); }
.grid.cols-2 { grid-template-columns: repeat(2, minmax(0,1fr)); }
.grid.cols-4 { grid-template-columns: repeat(4, minmax(0,1fr)); }
@media (max-width: 900px) {
  .grid.cols-3, .grid.cols-4 { grid-template-columns: repeat(2, minmax(0,1fr)); }
}
@media (max-width: 600px) {
  .grid.cols-2, .grid.cols-3, .grid.cols-4 { grid-template-columns: 1fr; }
  .nav-links { display: none; }
  .nav-toggle { display: inline-flex; }
  .site-nav .nav-links.open { display: flex; flex-direction: column; position: absolute; top: var(--nav-h); right: 0; left: 0; background: #fff; border-bottom: 1px solid var(--c-border-soft); padding: 10px 16px; }
}

/* ----- Numbered contribution items ----- */
.num-list { list-style: none; padding: 0; margin: 0; counter-reset: spark; }
.num-list li {
  counter-increment: spark;
  background: #fff; border: 1px solid var(--c-border-soft);
  border-radius: var(--radius-lg); padding: 20px 20px 20px 70px;
  position: relative; margin: 0 0 14px; box-shadow: var(--c-shadow);
}
.num-list li::before {
  content: counter(spark);
  position: absolute; left: 18px; top: 20px;
  width: 36px; height: 36px; border-radius: 50%;
  background: var(--c-primary-soft); color: var(--c-primary-deep);
  display: grid; place-items: center; font-weight: 800; font-size: 15px;
  border: 1px solid #d7e1f9;
}
.num-list li b { display: block; font-size: 16px; margin-bottom: 4px; color: var(--c-text); }
.num-list li span { color: var(--c-text-muted); font-size: 14.5px; }

/* ----- Stats row ----- */
.stats { display: grid; grid-template-columns: repeat(4, minmax(0,1fr)); gap: 16px; }
@media (max-width: 800px) { .stats { grid-template-columns: repeat(2, minmax(0,1fr)); } }
.stat {
  background: #fff; border: 1px solid var(--c-border-soft); border-radius: var(--radius-lg);
  padding: 22px; text-align: center; box-shadow: var(--c-shadow);
}
.stat .big {
  font-size: clamp(30px, 3.5vw, 44px); font-weight: 800;
  letter-spacing: -0.02em; color: var(--c-primary-deep);
}
.stat .label { color: var(--c-text-soft); font-size: 13.5px; text-transform: uppercase; letter-spacing: .1em; }

/* ----- Tag chips ----- */
.tag-row { display: flex; flex-wrap: wrap; gap: 8px; }
.tag { padding: 5px 11px; border-radius: 999px; background: var(--c-bg-soft);
  border: 1px solid var(--c-border-soft); color: var(--c-text-muted); font-size: 13px; }

/* ----- Image figure ----- */
figure.fig {
  margin: 0; background: #fff; border: 1px solid var(--c-border-soft);
  border-radius: var(--radius-lg); padding: 16px; box-shadow: var(--c-shadow);
}
figure.fig img { border-radius: 10px; margin: 0 auto; }
figure.fig figcaption { color: var(--c-text-muted); font-size: 13.5px; text-align: center; margin-top: 10px; }

/* Tight padding for very wide/short illustrative images (e.g. pipeline diagrams) */
figure.fig.fig-tight { padding: 6px 10px; }
figure.fig.fig-tight img { display: block; width: 100%; height: auto; }
figure.fig.fig-tight figcaption { margin-top: 8px; }

/* Full-width figure that breaks out of typical 2-col grids */
figure.fig.fig-wide { width: 100%; }
figure.fig.fig-wide img { width: 100%; height: auto; display: block; }

/* ----- Tabs ----- */
.tabs { display: flex; gap: 6px; flex-wrap: wrap; margin-bottom: 16px;
  padding: 6px; background: var(--c-bg-soft); border-radius: 999px; width: fit-content;
  border: 1px solid var(--c-border-soft);
}
.tabs button {
  border: 0; background: transparent; color: var(--c-text-muted);
  padding: 8px 14px; border-radius: 999px; cursor: pointer; font-weight: 600; font-size: 14px;
  transition: background .15s ease, color .15s ease;
}
.tabs button:hover { color: var(--c-text); }
.tabs button.active { background: var(--c-primary); color: #fff; }
.tab-panel { display: none; }
.tab-panel.active { display: block; animation: fadeUp .25s ease; }
@keyframes fadeUp { from { opacity: 0; transform: translateY(6px);} to { opacity: 1; transform: none;} }

/* ----- Table ----- */
.table-wrap { overflow-x: auto; border: 1px solid var(--c-border-soft); border-radius: var(--radius-lg); background: #fff; }
table.sk { border-collapse: collapse; width: 100%; font-size: 14.5px; }
table.sk th, table.sk td { padding: 11px 14px; text-align: left; border-bottom: 1px solid var(--c-border-soft); }
table.sk thead th { background: var(--c-bg-soft); color: var(--c-text); font-weight: 700; font-size: 13px; text-transform: uppercase; letter-spacing: .08em; }
table.sk tbody tr:last-child td { border-bottom: 0; }
table.sk .best { background: #fff8e1; }
table.sk td.mono { font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-size: 13.5px; }
.badge-up { color: var(--c-success); font-weight: 700; }
.badge-down { color: var(--c-danger); font-weight: 700; }
.badge-neutral { color: var(--c-text-soft); font-weight: 600; }

/* ----- Quote / takeaway box ----- */
.takeaway {
  background: linear-gradient(180deg, #fff9e6 0%, #fffdf2 100%);
  border: 1px solid #f7e4a8;
  border-radius: var(--radius); padding: 14px 16px; color: #6b4d08;
  font-size: 15px;
}
.takeaway b { color: #8a5a00; }

.eqn {
  background: var(--c-bg-soft); border: 1px solid var(--c-border-soft);
  border-radius: var(--radius); padding: 14px 16px; font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: 14.5px; color: var(--c-text); overflow-x: auto;
}

/* ----- Prettified PDI equation ----- */
.eqn-box {
  display: inline-flex; align-items: center; flex-wrap: wrap;
  gap: 10px;
  padding: 22px 28px;
  background: linear-gradient(135deg, #f8fafc 0%, #eef2ff 55%, #fef3c7 100%);
  border: 1px solid #d7e1f9;
  border-radius: var(--radius-lg);
  box-shadow: var(--c-shadow);
  font-family: "Inter", "Times New Roman", Georgia, serif;
  font-size: 28px;
  line-height: 1;
  color: var(--c-text);
}
.eqn-box .eqn-kbd {
  font-weight: 800;
  letter-spacing: 0.02em;
  background: #fff;
  color: var(--c-primary-deep);
  border: 1px solid #c7d2fe;
  border-radius: 10px;
  padding: 6px 14px;
  font-size: 22px;
  box-shadow: 0 1px 0 rgba(15,23,42,0.04);
}
.eqn-box .eqn-eq { font-weight: 600; color: var(--c-text-muted); margin: 0 4px; }
.eqn-box .eqn-op { font-weight: 700; color: var(--c-text-muted); font-size: 26px; padding: 0 2px; }
.eqn-box .eqn-term {
  display: inline-flex; align-items: baseline;
  padding: 4px 8px;
  border-radius: 8px;
  transition: transform .2s ease;
}
.eqn-box .eqn-term:hover { transform: translateY(-1px); }
.eqn-box .eqn-term .eqn-z {
  font-style: italic; font-weight: 600;
  color: var(--c-text); margin-right: 1px;
}
.eqn-box .eqn-term .eqn-paren { color: var(--c-text-soft); }
.eqn-box .eqn-term .eqn-phi { font-style: italic; font-weight: 700; padding: 0 2px; }
.eqn-box .eqn-pos .eqn-phi { color: #15803d; }
.eqn-box .eqn-neg .eqn-phi { color: #b45309; }
.eqn-box .eqn-phi sub { font-size: 0.58em; font-style: normal; font-weight: 600; letter-spacing: 0.02em; }
@media (max-width: 600px) {
  .eqn-box { font-size: 22px; padding: 16px 18px; gap: 6px; }
  .eqn-box .eqn-kbd { font-size: 18px; padding: 5px 10px; }
}

/* ----- Case study block ----- */
.case {
  background: #fff; border: 1px solid var(--c-border-soft);
  border-radius: var(--radius-lg); padding: 22px; box-shadow: var(--c-shadow);
}
.case h4 { margin: 0 0 6px; font-size: 17px; }
.case .case-meta { color: var(--c-text-soft); font-size: 13px; margin-bottom: 10px; }
.case .result {
  display: inline-block; background: var(--c-ok-soft); color: var(--c-success);
  border: 1px solid #bbf7d0; padding: 4px 10px; border-radius: 999px; font-size: 12.5px; font-weight: 700;
}

/* ----- Code block ----- */
pre.code {
  background: #0b1220; color: #e6edf3; border-radius: var(--radius);
  padding: 16px 18px; overflow: auto; font-size: 13px; line-height: 1.5;
  border: 1px solid #0b1220;
}
pre.code code { font-family: ui-monospace, SFMono-Regular, Menlo, monospace; }

.bibtex-wrap { position: relative; }
.bibtex-wrap .copy-btn {
  position: absolute; top: 10px; right: 10px;
  background: rgba(255,255,255,0.08); color: #e6edf3;
  border: 1px solid rgba(255,255,255,0.18); border-radius: 8px;
  padding: 6px 10px; font-size: 12px; cursor: pointer;
}
.bibtex-wrap .copy-btn:hover { background: rgba(255,255,255,0.16); }

/* ----- Footer ----- */
.site-footer {
  padding: 40px 0 60px; border-top: 1px solid var(--c-border-soft);
  background: var(--c-bg-soft); color: var(--c-text-muted); font-size: 14px;
}
.site-footer .wrap { display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: 12px; }
.site-footer a { color: var(--c-text-muted); }
.site-footer a:hover { color: var(--c-text); }

/* ----- Utility ----- */
.mt-8 { margin-top: 8px; } .mt-16 { margin-top: 16px; } .mt-24 { margin-top: 24px; } .mt-32 { margin-top: 32px; }
.center { text-align: center; }
.small { font-size: 13.5px; color: var(--c-text-soft); }
.divider { height: 1px; background: var(--c-border-soft); margin: 26px 0; }

.kbd {
  display: inline-block; padding: 2px 6px; border: 1px solid var(--c-border);
  border-bottom-width: 2px; border-radius: 6px; background: #fff;
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-size: 12.5px;
}