/* UrbanTwin Sim2Real LiDAR Challenge — IEEE BigData 2026 Cup */
:root {
  --ink-950: #0b0e17;
  --ink-900: #10141f;
  --ink-800: #171c2b;
  --ink-700: #232a3d;
  --line: #2b3348;
  --text: #dde3f0;
  --text-dim: #97a1b8;
  --lumpi: #ffb454;   /* LUMPI amber */
  --v2x: #4fd6e0;     /* V2X-Real cyan */
  --accent: #8ea2ff;  /* shared indigo accent */
  --radius: 10px;
  --maxw: 1080px;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: 84px; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation: none !important; transition: none !important; }
}

body {
  background: var(--ink-950);
  color: var(--text);
  font-family: "Inter", system-ui, -apple-system, "Segoe UI", sans-serif;
  font-size: 16.5px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4 { font-family: "Space Grotesk", "Inter", sans-serif; line-height: 1.15; letter-spacing: -0.015em; }
code, pre, .mono { font-family: "IBM Plex Mono", ui-monospace, Consolas, monospace; }

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
a:focus-visible, button:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; border-radius: 3px; }

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

/* ---------- nav ---------- */
.nav {
  position: sticky; top: 0; z-index: 50;
  background: rgba(11, 14, 23, 0.86);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}
.nav-inner { display: flex; align-items: center; gap: 20px; height: 64px; max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }
.nav-brand { display: flex; align-items: center; gap: 10px; font-family: "Space Grotesk", sans-serif; font-weight: 700; color: var(--text); font-size: 1.02rem; white-space: nowrap; }
.nav-brand img { width: 28px; height: 28px; border-radius: 6px; }
.nav-logo { display: block; align-self: center; height: 36px; width: auto; border-radius: 6px; }
@media (max-width: 760px) { .nav-logo { display: none; } }
.nav-brand:hover { text-decoration: none; }
.nav-links { display: flex; gap: 18px; margin-left: auto; flex-wrap: wrap; }
.nav-links a { color: var(--text-dim); font-size: 0.92rem; }
.nav-links a:hover { color: var(--text); text-decoration: none; }
.nav-links a.track-lumpi { color: var(--lumpi); }
.nav-links a.track-v2x { color: var(--v2x); }

/* ---------- hero ---------- */
.hero { position: relative; overflow: hidden; border-bottom: 1px solid var(--line); }
.hero-inner { position: relative; z-index: 2; max-width: var(--maxw); margin: 0 auto; padding: 96px 24px 88px; }
.eyebrow {
  display: inline-block; font-family: "IBM Plex Mono", monospace; font-size: 0.78rem;
  letter-spacing: 0.14em; text-transform: uppercase; color: var(--accent);
  border: 1px solid var(--line); border-radius: 999px; padding: 6px 14px;
  background: rgba(23, 28, 43, 0.7); margin-bottom: 26px;
}
.hero h1 { font-size: clamp(1.2rem, 3.8vw, 2.8rem); font-weight: 700; max-width: none; white-space: nowrap; }
.hero p.org-line, .track-hero p.org-line { margin: 0 0 14px; font-size: clamp(0.78rem, 1.7vw, 0.98rem); max-width: none; white-space: nowrap; }
.hero h1 .thin { color: var(--text-dim); font-weight: 500; }
.hero .sub { margin-top: 20px; max-width: 640px; color: var(--text-dim); font-size: 1.08rem; }
.hero-ctas { display: flex; gap: 14px; margin-top: 34px; flex-wrap: wrap; }

.btn {
  display: inline-block; padding: 12px 22px; border-radius: var(--radius);
  font-family: "Space Grotesk", sans-serif; font-weight: 600; font-size: 0.98rem;
  border: 1px solid var(--line); color: var(--text); background: var(--ink-800);
  transition: transform 0.15s ease, border-color 0.15s ease;
}
.btn:hover { text-decoration: none; transform: translateY(-2px); border-color: var(--text-dim); }
.btn-lumpi { background: linear-gradient(135deg, #3a2a12, #241a0c); border-color: #6b4d1e; color: var(--lumpi); }
.btn-lumpi:hover { border-color: var(--lumpi); }
.btn-v2x { background: linear-gradient(135deg, #0e2f33, #0a1f24); border-color: #1e5b62; color: var(--v2x); }
.btn-v2x:hover { border-color: var(--v2x); }

.hero-facts { display: flex; gap: 34px; margin-top: 44px; flex-wrap: wrap; }
.fact .k { font-family: "IBM Plex Mono", monospace; font-size: 0.74rem; letter-spacing: 0.12em; text-transform: uppercase; color: var(--text-dim); }
.fact .v { font-family: "Space Grotesk", sans-serif; font-size: 1.12rem; font-weight: 600; margin-top: 2px; }

/* logo strip — sits before the title, matching its text height */
.title-row { display: flex; align-items: center; gap: 20px; }
.logo-strip { display: flex; align-items: center; gap: 12px; flex-shrink: 0; }
.logo-strip a { display: block; line-height: 0; }
.logo-strip img { display: block; height: clamp(2.2rem, 6.6vw, 5rem); width: auto; border-radius: 10px; border: 1px solid var(--line); background: var(--ink-900); }
.title-row h1 { font-size: clamp(1.05rem, 2.9vw, 2.2rem); }
.logo-strip a:hover img { border-color: var(--text-dim); }
@media (max-width: 640px) { .title-row { flex-wrap: wrap; } .logo-strip img { height: 56px; } }

/* hero dates timeline strip */
.hero-dates { margin-top: 34px; border-top: 2px solid var(--line); padding-top: 18px; display: grid; grid-template-columns: repeat(6, auto); justify-content: space-between; gap: 14px; }
.hero-dates .fact .k { font-size: clamp(0.58rem, 0.85vw, 0.74rem); white-space: nowrap; }
.hero-dates .fact .v { font-size: clamp(0.78rem, 1.25vw, 1.05rem); white-space: nowrap; }
.hero-dates .fact { position: relative; }
.hero-dates .fact::before {
  content: ""; position: absolute; top: -25px; left: 1px;
  width: 12px; height: 12px; border-radius: 50%;
  background: var(--ink-950); border: 2px solid var(--accent);
}
.hero-dates .fact:nth-child(4)::before { background: var(--accent); } /* final deadline emphasized */

/* hero background — real vs synthetic frames from the UrbanTwin paper,
   each drawn in by its own scan line */
.hero-bg {
  position: absolute; inset: 0; z-index: 0;
  display: grid; grid-template-columns: 1fr 1fr; grid-template-rows: 1fr 1fr; gap: 3px;
}
.hero-bg .cell { position: relative; overflow: hidden; background: var(--ink-950); }
.hero-bg img {
  width: 100%; height: 100%; object-fit: cover; display: block;
  clip-path: inset(0 100% 0 0);
  animation: hf-draw 18s linear infinite;
}
.hero-bg .cell::after {
  content: ""; position: absolute; top: 0; bottom: 0; left: 0; width: 3px; opacity: 0;
  animation: hf-line 18s linear infinite;
}
.hero-bg .lumpi-cell::after { background: var(--lumpi); box-shadow: 0 0 18px 3px rgba(255,180,84,0.55); }
.hero-bg .v2x-cell::after { background: var(--v2x); box-shadow: 0 0 18px 3px rgba(79,214,224,0.55); }
.hero-bg .cell:nth-child(1) img, .hero-bg .cell:nth-child(1)::after, .hero-bg .cell:nth-child(1) .cell-label { animation-delay: 0s; }
.hero-bg .cell:nth-child(2) img, .hero-bg .cell:nth-child(2)::after, .hero-bg .cell:nth-child(2) .cell-label { animation-delay: 4.5s; }
.hero-bg .cell:nth-child(3) img, .hero-bg .cell:nth-child(3)::after, .hero-bg .cell:nth-child(3) .cell-label { animation-delay: 9s; }
.hero-bg .cell:nth-child(4) img, .hero-bg .cell:nth-child(4)::after, .hero-bg .cell:nth-child(4) .cell-label { animation-delay: 13.5s; }
.cell-label {
  position: absolute; top: 50%; left: 0; opacity: 0;
  transform: translate(calc(-100% - 14px), -50%);
  font-family: "IBM Plex Mono", monospace; font-size: 0.78rem; font-weight: 500;
  letter-spacing: 0.16em; text-transform: uppercase; white-space: nowrap;
  animation: hf-label 18s linear infinite;
}
.lumpi-cell .cell-label { color: var(--lumpi); text-shadow: 0 0 12px rgba(255,180,84,0.8); }
.v2x-cell .cell-label { color: var(--v2x); text-shadow: 0 0 12px rgba(79,214,224,0.8); }
@keyframes hf-label {
  0%    { left: 0%;               opacity: 0; }
  2%    { opacity: 1; }
  20%   { opacity: 1; }
  21.9% { left: calc(100% - 3px); opacity: 1; }
  22%   { opacity: 0; }
  100%  { left: calc(100% - 3px); opacity: 0; }
}
@keyframes hf-draw {
  0%   { clip-path: inset(0 100% 0 0); opacity: 1; }
  22%  { clip-path: inset(0 0 0 0);    opacity: 1; }
  90%  { clip-path: inset(0 0 0 0);    opacity: 1; }
  99%  { clip-path: inset(0 0 0 0);    opacity: 0; }
  100% { clip-path: inset(0 100% 0 0); opacity: 0; }
}
@keyframes hf-line {
  0%    { left: 0%;              opacity: 1; }
  21.9% { left: calc(100% - 3px); opacity: 1; }
  22%   { opacity: 0; }
  100%  { left: calc(100% - 3px); opacity: 0; }
}
.hero-shade {
  position: absolute; inset: 0; z-index: 1;
  background:
    linear-gradient(90deg, rgba(11,14,23,0.94) 0%, rgba(11,14,23,0.82) 45%, rgba(11,14,23,0.55) 100%),
    linear-gradient(180deg, rgba(11,14,23,0.35) 0%, transparent 40%, rgba(11,14,23,0.85) 100%);
}
@media (prefers-reduced-motion: reduce) {
  .hero-bg img { animation: none; clip-path: none; opacity: 0.9; }
  .hero-bg .cell::after { display: none; }
  .cell-label { animation: none; opacity: 0.45; }
}

/* ---------- sections ---------- */
section { padding: 72px 0; border-bottom: 1px solid var(--line); }
section:last-of-type { border-bottom: none; }
.sec-label { font-family: "IBM Plex Mono", monospace; font-size: 0.76rem; letter-spacing: 0.16em; text-transform: uppercase; color: var(--accent); margin-bottom: 12px; }
section h2 { font-size: clamp(1.5rem, 3vw, 2.1rem); margin-bottom: 18px; }
section .lede { color: var(--text-dim); max-width: 700px; margin-bottom: 30px; }

/* track cards */
.tracks { display: grid; grid-template-columns: 1fr 1fr; gap: 22px; }
.track-card {
  border: 1px solid var(--line); border-radius: var(--radius); background: var(--ink-900);
  padding: 30px 28px; position: relative; overflow: hidden; display: flex; flex-direction: column;
}
.track-card::before { content: ""; position: absolute; top: 0; left: 0; right: 0; height: 3px; }
.track-card.lumpi::before { background: var(--lumpi); }
.track-card.v2x::before { background: var(--v2x); }
.track-card .tag { font-family: "IBM Plex Mono", monospace; font-size: 0.74rem; letter-spacing: 0.12em; text-transform: uppercase; }
.track-card.lumpi .tag { color: var(--lumpi); }
.track-card.v2x .tag { color: var(--v2x); }
.track-card h3 { font-size: 1.4rem; margin: 10px 0 12px; }
.track-card p { color: var(--text-dim); font-size: 0.97rem; flex: 1; }
.track-meta { margin: 18px 0 22px; display: grid; gap: 8px; font-size: 0.92rem; }
.track-meta div { display: flex; gap: 10px; }
.track-meta .mk { font-family: "IBM Plex Mono", monospace; color: var(--text-dim); min-width: 96px; font-size: 0.82rem; padding-top: 2px; }
.track-actions { display: flex; gap: 12px; flex-wrap: wrap; }
.btn-sm { padding: 9px 16px; font-size: 0.9rem; }

/* steps */
.steps { display: grid; grid-template-columns: repeat(4, 1fr); gap: 18px; counter-reset: step; }
.step { border: 1px solid var(--line); border-radius: var(--radius); background: var(--ink-900); padding: 22px 20px; }
.step::before {
  counter-increment: step; content: counter(step, decimal-leading-zero);
  font-family: "IBM Plex Mono", monospace; color: var(--accent); font-size: 0.8rem; letter-spacing: 0.1em;
}
.step h4 { margin: 8px 0 8px; font-size: 1.02rem; }
.step p { color: var(--text-dim); font-size: 0.9rem; }

/* scoring */
.score-formula {
  border: 1px solid var(--line); border-radius: var(--radius); background: var(--ink-900);
  padding: 26px 28px; font-family: "IBM Plex Mono", monospace; font-size: 0.95rem;
  overflow-x: auto; margin-bottom: 26px; white-space: pre;
}
.score-formula .w60 { color: var(--lumpi); }
.score-formula .w40 { color: var(--v2x); }
.metric-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; }
.metric { border: 1px solid var(--line); border-radius: var(--radius); background: var(--ink-900); padding: 18px; }
.metric .abbr { font-family: "Space Grotesk", sans-serif; font-weight: 700; font-size: 1.2rem; color: var(--accent); }
.metric p { font-size: 0.86rem; color: var(--text-dim); margin-top: 6px; }

/* timeline */
.timeline { list-style: none; border-left: 2px solid var(--line); margin-left: 8px; }
.timeline li { position: relative; padding: 0 0 26px 28px; }
.timeline li::before {
  content: ""; position: absolute; left: -7px; top: 6px; width: 12px; height: 12px;
  border-radius: 50%; background: var(--ink-950); border: 2px solid var(--accent);
}
.timeline li.milestone::before { background: var(--accent); }
.timeline .date { font-family: "IBM Plex Mono", monospace; font-size: 0.82rem; color: var(--accent); letter-spacing: 0.05em; }
.timeline .what { font-weight: 600; font-family: "Space Grotesk", sans-serif; }
.timeline .note { color: var(--text-dim); font-size: 0.92rem; }

/* tables */
.table-scroll { overflow-x: auto; }
table { border-collapse: collapse; width: 100%; font-size: 0.94rem; }
th, td { border: 1px solid var(--line); padding: 10px 14px; text-align: left; }
th { background: var(--ink-800); font-family: "Space Grotesk", sans-serif; font-size: 0.88rem; }
td { background: var(--ink-900); }
td .mono, th .mono { font-size: 0.85rem; }

/* prizes */
.prizes { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; max-width: 720px; }
.prize { border: 1px solid var(--line); border-radius: var(--radius); background: var(--ink-900); padding: 24px; text-align: center; }
.prize .place { font-family: "IBM Plex Mono", monospace; font-size: 0.78rem; letter-spacing: 0.14em; text-transform: uppercase; color: var(--text-dim); }
.prize .amount { font-family: "Space Grotesk", sans-serif; font-size: 2rem; font-weight: 700; margin-top: 6px; }
.prize:nth-child(1) .amount { color: var(--lumpi); }

/* rules */
.rule-cols { display: grid; grid-template-columns: 1fr 1fr; gap: 22px; }
.rule-box { border: 1px solid var(--line); border-radius: var(--radius); background: var(--ink-900); padding: 26px 28px; }
.rule-box h3 { font-size: 1.1rem; margin-bottom: 14px; }
.rule-box.allowed h3 { color: #7ee08a; }
.rule-box.forbidden h3 { color: #ff7a7a; }
.rule-box ul { margin-left: 18px; color: var(--text-dim); font-size: 0.95rem; display: grid; gap: 10px; }

/* generic content blocks (track pages) */
.content h2 { font-size: 1.5rem; margin: 44px 0 14px; }
.content h3 { font-size: 1.12rem; margin: 26px 0 10px; color: var(--text); }
.content p, .content li { color: var(--text-dim); }
.content p { margin-bottom: 14px; }
.content ul, .content ol { margin: 0 0 16px 22px; display: grid; gap: 8px; }
.content pre {
  background: var(--ink-900); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 18px 20px; overflow-x: auto; font-size: 0.88rem; margin: 14px 0 20px; line-height: 1.55;
}
.content code { background: var(--ink-800); border: 1px solid var(--line); border-radius: 4px; padding: 1px 6px; font-size: 0.86em; }
.content pre code { background: none; border: none; padding: 0; }
.content blockquote { border-left: 3px solid var(--accent); padding: 6px 18px; background: var(--ink-900); border-radius: 0 var(--radius) var(--radius) 0; margin: 14px 0 18px; font-style: italic; }
.content table { margin: 8px 0 20px; }

/* track page hero */
.track-hero { border-bottom: 1px solid var(--line); padding: 70px 0 54px; position: relative; overflow: hidden; }
.track-hero.lumpi { background: radial-gradient(900px 340px at 15% 0%, rgba(255, 180, 84, 0.10), transparent 70%), var(--ink-950); }
.track-hero.v2x { background: radial-gradient(900px 340px at 15% 0%, rgba(79, 214, 224, 0.10), transparent 70%), var(--ink-950); }
.track-hero h1 { font-size: clamp(1.8rem, 4vw, 2.7rem); max-width: 780px; }
.track-hero .sub { color: var(--text-dim); margin-top: 14px; max-width: 660px; }
.track-hero .hero-ctas { margin-top: 28px; }
.track-hero .eyebrow.lumpi { color: var(--lumpi); }
.track-hero .eyebrow.v2x { color: var(--v2x); }

/* reference lists: bold title line, description on its own line */
.ref-list { list-style: none; margin-left: 0 !important; gap: 16px !important; }
.ref-list li { border-left: 2px solid var(--line); padding-left: 16px; }
.ref-list li > a { display: block; line-height: 1.4; }
.ref-list .ref-desc { display: block; color: var(--text-dim); font-size: 0.93rem; margin-top: 3px; }

/* citations */
details.bib { border: 1px solid var(--line); border-radius: var(--radius); background: var(--ink-900); margin-bottom: 12px; }
details.bib summary { cursor: pointer; padding: 14px 18px; font-family: "Space Grotesk", sans-serif; font-weight: 600; font-size: 0.98rem; }
details.bib pre { margin: 0 18px 16px; white-space: pre-wrap; }

/* organizers / footer */
.orgs { display: flex; gap: 22px; flex-wrap: wrap; }
.org { border: 1px solid var(--line); border-radius: var(--radius); background: var(--ink-900); padding: 22px 26px; min-width: 260px; }
.org .name { font-family: "Space Grotesk", sans-serif; font-weight: 700; font-size: 1.05rem; }
.org .aff { color: var(--text-dim); font-size: 0.92rem; }

footer { border-top: 1px solid var(--line); padding: 36px 0 48px; color: var(--text-dim); font-size: 0.9rem; }
footer .wrap { display: flex; justify-content: space-between; gap: 20px; flex-wrap: wrap; }

.notice {
  border: 1px solid #6b4d1e; background: rgba(255, 180, 84, 0.06); border-radius: var(--radius);
  padding: 14px 18px; font-size: 0.92rem; color: var(--text-dim); margin-top: 24px;
}
.notice strong { color: var(--lumpi); }

@media (max-width: 900px) {
  .steps, .metric-grid { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 640px) {
  .tracks, .rule-cols, .steps, .metric-grid, .prizes { grid-template-columns: 1fr; }
  .hero h1, .hero p.org-line { white-space: normal; }
  .hero-dates { grid-template-columns: repeat(2, auto); row-gap: 20px; }
  .nav-links { gap: 12px; }
  .hero-inner { padding: 70px 24px 60px; }
}