/* ==========================================================================
   The Last Leap Second — design system
   ========================================================================== */

:root {
  color-scheme: dark;
  --bg: #070a16;
  --bg-2: #0a0f22;
  --panel: #101731;
  --panel-2: #151d3b;
  --panel-3: #1b2450;
  --line: #26315c;
  --line-soft: #1c2547;
  --ink: #eef2ff;
  --muted: #96a2c9;
  --muted-2: #6f7ca6;
  --atomic: #ffc24b;
  --atomic-soft: rgba(255, 194, 75, 0.14);
  --earth: #46d6c5;
  --earth-soft: rgba(70, 214, 197, 0.14);
  --ok: #4bd68f;
  --alert: #ff5d6c;
  --alert-soft: rgba(255, 93, 108, 0.14);
  --accent: #8f9bff;
  --shadow: 0 18px 50px -22px rgba(0, 0, 0, 0.85);
  --radius: 16px;
  --radius-sm: 10px;
  --maxw: 1140px;
  --mono: "IBM Plex Mono", ui-monospace, SFMono-Regular, Menlo, monospace;
  --sans: "Space Grotesk", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}

html[data-theme="light"] {
  color-scheme: light;
  --bg: #f3f0e6;
  --bg-2: #ece7d8;
  --panel: #fffdf7;
  --panel-2: #f8f4e9;
  --panel-3: #f1ebdb;
  --line: #d9d1bd;
  --line-soft: #e6dfcd;
  --ink: #141a2c;
  --muted: #5a637f;
  --muted-2: #7b849c;
  --atomic: #a86a10;
  --atomic-soft: rgba(168, 106, 16, 0.12);
  --earth: #0e8a7d;
  --earth-soft: rgba(14, 138, 125, 0.12);
  --ok: #1b8451;
  --alert: #cc3746;
  --alert-soft: rgba(204, 55, 70, 0.12);
  --accent: #4b55c9;
  --shadow: 0 18px 44px -26px rgba(40, 34, 12, 0.55);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  z-index: -1;
  pointer-events: none;
  background:
    radial-gradient(1100px 620px at 78% -6%, rgba(70, 214, 197, 0.10), transparent 60%),
    radial-gradient(900px 540px at 6% 4%, rgba(255, 194, 75, 0.09), transparent 62%);
}
html[data-theme="light"] body::before {
  background:
    radial-gradient(1100px 620px at 78% -6%, rgba(14, 138, 125, 0.10), transparent 60%),
    radial-gradient(900px 540px at 6% 4%, rgba(168, 106, 16, 0.10), transparent 62%);
}

img, svg, canvas { max-width: 100%; }
a { color: inherit; }

h1, h2, h3, h4 { line-height: 1.08; margin: 0 0 0.5em; font-weight: 600; letter-spacing: -0.015em; }
p { margin: 0 0 1em; }

.mono { font-family: var(--mono); font-variant-numeric: tabular-nums; }

.container { width: 100%; max-width: var(--maxw); margin: 0 auto; padding: 0 20px; }
.narrow { max-width: 760px; }

.eyebrow {
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.24em;
  text-transform: uppercase;
  color: var(--atomic);
  margin: 0 0 0.9rem;
  display: inline-flex;
  align-items: center;
  gap: 0.6em;
}
.eyebrow::before {
  content: "";
  width: 26px; height: 1px;
  background: var(--atomic);
  display: inline-block;
  opacity: 0.8;
}

.lead { font-size: 1.16rem; color: var(--muted); max-width: 62ch; }
.muted { color: var(--muted); }
.small { font-size: 0.86rem; }
.tiny { font-size: 0.76rem; }
.center { text-align: center; }
.wrap { flex-wrap: wrap; }

/* ---------------------------------------------------------------- header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  backdrop-filter: blur(12px);
  background: color-mix(in srgb, var(--bg) 82%, transparent);
  border-bottom: 1px solid var(--line-soft);
}
.site-header .container {
  display: flex;
  align-items: center;
  gap: 18px;
  min-height: 62px;
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 11px;
  text-decoration: none;
  font-weight: 600;
  letter-spacing: -0.01em;
  margin-right: auto;
  white-space: nowrap;
}
.brand svg { width: 28px; height: 28px; flex: none; }
.brand b { font-weight: 600; }
.brand span { color: var(--muted); font-weight: 400; }

.site-nav { display: flex; align-items: center; gap: 4px; flex-wrap: wrap; }
.site-nav a {
  text-decoration: none;
  color: var(--muted);
  font-size: 0.9rem;
  padding: 7px 11px;
  border-radius: 9px;
  transition: color 0.15s, background 0.15s;
}
.site-nav a:hover { color: var(--ink); background: var(--panel-2); }
.site-nav a[aria-current="page"] { color: var(--ink); background: var(--panel-3); }

.icon-btn {
  appearance: none;
  border: 1px solid var(--line);
  background: var(--panel);
  color: var(--ink);
  width: 38px; height: 36px;
  border-radius: 10px;
  cursor: pointer;
  display: inline-grid;
  place-items: center;
  transition: border-color 0.15s, transform 0.15s;
}
.icon-btn:hover { border-color: var(--atomic); }
.icon-btn:active { transform: scale(0.95); }
.icon-btn svg { width: 18px; height: 18px; }

/* ---------------------------------------------------------------- buttons */
.btn {
  appearance: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.55em;
  font-family: var(--sans);
  font-size: 0.95rem;
  font-weight: 600;
  padding: 12px 20px;
  border-radius: 12px;
  border: 1px solid var(--line);
  background: var(--panel-2);
  color: var(--ink);
  cursor: pointer;
  text-decoration: none;
  transition: transform 0.14s, border-color 0.14s, background 0.14s, box-shadow 0.14s;
  line-height: 1;
}
.btn:hover { border-color: var(--accent); transform: translateY(-1px); }
.btn:active { transform: translateY(0) scale(0.99); }
.btn-primary {
  background: linear-gradient(160deg, #ffc24b, #ff9d4d);
  color: #1a1200;
  border-color: transparent;
  box-shadow: 0 12px 30px -14px rgba(255, 178, 60, 0.75);
}
.btn-primary:hover { box-shadow: 0 16px 36px -14px rgba(255, 178, 60, 0.9); }
.btn-ghost { background: transparent; }
.btn-lg { padding: 16px 28px; font-size: 1.05rem; border-radius: 14px; }
.btn:disabled { opacity: 0.45; cursor: not-allowed; transform: none; }
.btn svg { width: 18px; height: 18px; }

/* ---------------------------------------------------------------- layout */
section.band { padding: 62px 0; }
section.band.tight { padding: 40px 0; }
.section-head { max-width: 70ch; margin-bottom: 30px; }

.grid { display: grid; gap: 18px; }
.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-4 { grid-template-columns: repeat(4, 1fr); }

.card {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 22px;
  position: relative;
}
.card h3 { margin-bottom: 0.35em; }
.card p:last-child { margin-bottom: 0; }
.card .tag {
  font-family: var(--mono);
  font-size: 0.68rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--earth);
  display: block;
  margin-bottom: 0.7em;
}
a.card { text-decoration: none; transition: border-color 0.15s, transform 0.15s; }
a.card:hover { border-color: var(--atomic); transform: translateY(-2px); }

/* ---------------------------------------------------------------- hero */
.hero { padding: 54px 0 20px; }
.hero-grid {
  display: grid;
  grid-template-columns: 1.05fr 0.95fr;
  gap: 44px;
  align-items: center;
}
.hero h1 {
  font-size: clamp(2.1rem, 5.6vw, 3.6rem);
  letter-spacing: -0.03em;
  margin-bottom: 0.4em;
}
.hero h1 .gold {
  background: linear-gradient(100deg, var(--atomic), #ff9d4d);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.hero .lead { font-size: 1.18rem; }
.hero-actions { display: flex; gap: 12px; flex-wrap: wrap; margin-top: 26px; }

.chips { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 26px; }
.chip {
  font-family: var(--mono);
  font-size: 0.74rem;
  letter-spacing: 0.04em;
  color: var(--muted);
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 5px 11px;
  background: var(--panel);
}
.chip b { color: var(--ink); font-weight: 600; }

/* ---------------------------------------------------------------- game */
.game-shell {
  background: linear-gradient(180deg, var(--panel), var(--bg-2));
  border: 1px solid var(--line);
  border-radius: 22px;
  padding: 20px;
  box-shadow: var(--shadow);
}
.game-stage {
  position: relative;
  width: 100%;
  aspect-ratio: 1 / 1;
  max-width: 560px;
  margin: 0 auto;
  touch-action: manipulation;
  cursor: pointer;
}
.game-stage canvas { width: 100%; height: 100%; display: block; }

.hud {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
  margin-bottom: 14px;
}
.hud .cell {
  background: var(--bg-2);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 9px 11px;
}
.hud .cell .k {
  font-family: var(--mono);
  font-size: 0.62rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--muted-2);
  display: block;
  margin-bottom: 2px;
}
.hud .cell .v { font-family: var(--mono); font-size: 1.12rem; font-weight: 600; }

.game-controls { display: flex; gap: 10px; align-items: center; margin-top: 14px; flex-wrap: wrap; }
.game-controls .grow { flex: 1 1 auto; }

.overlay {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  text-align: center;
  padding: 20px;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(6px);
  border-radius: 22px;
  overflow-y: auto;
  z-index: 5;
}
.overlay .panel { max-width: 400px; margin: auto; }
.overlay h3 { font-size: 1.5rem; margin-bottom: 0.35em; }
.overlay p { color: var(--muted); font-size: 0.95rem; }
.overlay .btn { margin-top: 8px; }
.overlay[hidden] { display: none; }

.mode-badge {
  font-family: var(--mono);
  font-size: 0.68rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--earth);
}

.legend { display: flex; gap: 16px; flex-wrap: wrap; margin-top: 14px; font-size: 0.82rem; color: var(--muted); }
.legend span { display: inline-flex; align-items: center; gap: 7px; }
.dot { width: 10px; height: 10px; border-radius: 50%; display: inline-block; }
.dot.atomic { background: var(--atomic); }
.dot.earth { background: var(--earth); }
.dot.alert { background: var(--alert); }

/* ---------------------------------------------------------------- readouts */
.readout {
  font-family: var(--mono);
  font-variant-numeric: tabular-nums;
  background: var(--bg-2);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 16px;
}
.readout .row { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: baseline; gap: 8px 12px; padding: 7px 0; border-bottom: 1px dashed var(--line-soft); }
.readout .row:last-child { border-bottom: 0; }
.readout .row .label { color: var(--muted); font-size: 0.82rem; letter-spacing: 0.04em; }
.readout .row .val { font-size: 1.25rem; font-weight: 600; }
.big-clock { font-size: clamp(2rem, 7vw, 3.1rem); font-weight: 600; letter-spacing: 0.02em; }

/* ---------------------------------------------------------------- timeline (leap seconds) */
.ls-ring { display: block; margin: 0 auto; }
.ls-list { display: grid; gap: 6px; max-height: 430px; overflow-y: auto; padding-right: 6px; }
.ls-item {
  display: grid;
  grid-template-columns: 44px 1fr auto;
  gap: 12px;
  align-items: center;
  padding: 9px 12px;
  border: 1px solid var(--line-soft);
  border-radius: 10px;
  background: var(--panel);
  cursor: pointer;
  transition: border-color 0.12s, background 0.12s;
}
.ls-item:hover, .ls-item[aria-current="true"] { border-color: var(--atomic); background: var(--panel-2); }
.ls-item .num { font-family: var(--mono); color: var(--atomic); font-weight: 600; }
.ls-item .dt { font-family: var(--mono); font-size: 0.86rem; }
.ls-item .off { font-family: var(--mono); color: var(--muted); font-size: 0.82rem; }

/* ---------------------------------------------------------------- horizontal timeline */
.tl { position: relative; margin-top: 10px; }
.tl-item {
  position: relative;
  padding: 0 0 26px 30px;
  border-left: 1px solid var(--line);
}
.tl-item:last-child { border-left-color: transparent; padding-bottom: 0; }
.tl-item::before {
  content: "";
  position: absolute;
  left: -5px; top: 5px;
  width: 9px; height: 9px;
  border-radius: 50%;
  background: var(--earth);
  box-shadow: 0 0 0 4px color-mix(in srgb, var(--earth) 22%, transparent);
}
.tl-item[data-tag="Atomic"]::before { background: var(--atomic); box-shadow: 0 0 0 4px color-mix(in srgb, var(--atomic) 22%, transparent); }
.tl-item[data-tag="Reform"]::before { background: var(--alert); box-shadow: 0 0 0 4px color-mix(in srgb, var(--alert) 22%, transparent); }
.tl-year { font-family: var(--mono); font-size: 0.82rem; color: var(--atomic); letter-spacing: 0.06em; }
.tl-item h3 { font-size: 1.06rem; margin: 0.15em 0 0.25em; }
.tl-item p { color: var(--muted); font-size: 0.94rem; margin: 0; }

/* ---------------------------------------------------------------- stat tiles */
.stat {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px;
}
.stat .num { font-family: var(--mono); font-size: clamp(1.6rem, 5vw, 2.2rem); font-weight: 600; color: var(--atomic); }
.stat .lbl { font-size: 0.86rem; color: var(--muted); }

/* ---------------------------------------------------------------- quiz */
.quiz-card { max-width: 720px; margin: 0 auto; }
.q-progress { display: flex; gap: 5px; margin-bottom: 20px; }
.q-progress i { flex: 1; height: 5px; border-radius: 3px; background: var(--line); transition: background 0.2s; }
.q-progress i.done { background: var(--earth); }
.q-progress i.good { background: var(--ok); }
.q-progress i.bad { background: var(--alert); }
.q-count { font-family: var(--mono); color: var(--muted); font-size: 0.82rem; letter-spacing: 0.1em; }
.q-text { font-size: 1.3rem; font-weight: 600; margin: 8px 0 18px; }
.q-options { display: grid; gap: 10px; }
.opt {
  text-align: left;
  padding: 14px 16px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--panel-2);
  color: var(--ink);
  font-size: 1rem;
  font-family: var(--sans);
  cursor: pointer;
  transition: border-color 0.12s, background 0.12s, transform 0.12s;
}
.opt:hover:not(:disabled) { border-color: var(--accent); transform: translateX(2px); }
.opt:disabled { cursor: default; }
.opt.correct { border-color: var(--ok); background: color-mix(in srgb, var(--ok) 16%, var(--panel)); }
.opt.wrong { border-color: var(--alert); background: color-mix(in srgb, var(--alert) 16%, var(--panel)); }
.opt .key { font-family: var(--mono); color: var(--muted); margin-right: 10px; }
.explain {
  margin-top: 18px;
  padding: 16px;
  border-left: 3px solid var(--earth);
  background: var(--panel-2);
  border-radius: 0 12px 12px 0;
  font-size: 0.95rem;
}
.explain .src { display: block; margin-top: 8px; color: var(--muted-2); font-size: 0.78rem; font-family: var(--mono); }

/* ---------------------------------------------------------------- footer */
.site-footer {
  border-top: 1px solid var(--line-soft);
  margin-top: 40px;
  padding: 42px 0 60px;
  color: var(--muted);
  font-size: 0.9rem;
}
.site-footer .cols { display: grid; grid-template-columns: 1.4fr 1fr 1fr; gap: 28px; }
.site-footer h4 { color: var(--ink); font-size: 0.95rem; margin-bottom: 0.8em; }
.site-footer a { color: var(--muted); text-decoration: none; display: block; padding: 3px 0; }
.site-footer a:hover { color: var(--atomic); }
.site-footer .fine { margin-top: 30px; padding-top: 20px; border-top: 1px solid var(--line-soft); font-size: 0.8rem; color: var(--muted-2); }

/* ---------------------------------------------------------------- misc */
.toast {
  position: fixed;
  left: 50%; bottom: 26px;
  transform: translate(-50%, 20px);
  background: var(--ink);
  color: var(--bg);
  padding: 11px 18px;
  border-radius: 999px;
  font-size: 0.9rem;
  font-weight: 600;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.25s, transform 0.25s;
  z-index: 100;
}
.toast.show { opacity: 1; transform: translate(-50%, 0); }

.callout {
  border: 1px dashed var(--line);
  border-radius: var(--radius);
  padding: 18px 20px;
  background: var(--panel);
}
blockquote.pull {
  margin: 0;
  font-size: 1.3rem;
  line-height: 1.35;
  font-weight: 500;
  padding-left: 22px;
  border-left: 3px solid var(--atomic);
}
blockquote.pull cite { display: block; margin-top: 12px; font-size: 0.86rem; color: var(--muted); font-style: normal; font-family: var(--mono); }

.slider {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 6px;
  border-radius: 4px;
  background: linear-gradient(90deg, var(--earth), var(--atomic), var(--alert));
  outline: none;
}
.slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 24px; height: 24px;
  border-radius: 50%;
  background: var(--ink);
  border: 3px solid var(--atomic);
  cursor: pointer;
}
.slider::-moz-range-thumb {
  width: 22px; height: 22px;
  border-radius: 50%;
  background: var(--ink);
  border: 3px solid var(--atomic);
  cursor: pointer;
}

.table { width: 100%; border-collapse: collapse; font-size: 0.9rem; }
.table th, .table td { text-align: left; padding: 9px 10px; border-bottom: 1px solid var(--line-soft); }
.table th { font-family: var(--mono); font-size: 0.72rem; letter-spacing: 0.12em; text-transform: uppercase; color: var(--muted-2); }
.table td.num { font-family: var(--mono); }

.ls-split { display: grid; grid-template-columns: 320px 1fr; gap: 26px; align-items: start; }
@media (max-width: 760px) { .ls-split { grid-template-columns: 1fr; } }

.hidden { display: none !important; }
.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0;
}
:focus-visible { outline: 2px solid var(--atomic); outline-offset: 3px; border-radius: 6px; }

.share-row { display: flex; gap: 10px; flex-wrap: wrap; }

/* ---------------------------------------------------------------- responsive */
@media (max-width: 900px) {
  .hero-grid { grid-template-columns: 1fr; gap: 30px; }
  .grid-3, .grid-4 { grid-template-columns: repeat(2, 1fr); }
  .site-footer .cols { grid-template-columns: 1fr 1fr; }
  section.band { padding: 46px 0; }
}
@media (max-width: 640px) {
  body { font-size: 16px; }
  .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; }
  .hud { grid-template-columns: repeat(2, 1fr); }
  .site-header .container { min-height: 0; gap: 8px; padding-top: 10px; padding-bottom: 8px; flex-wrap: wrap; }
  .site-nav { order: 3; width: 100%; gap: 2px; }
  .site-nav a { padding: 6px 9px; font-size: 0.82rem; }
  .brand span { display: none; }
  .icon-btn { order: 2; }
  .hero-actions .btn { flex: 1 1 auto; }
  .site-footer .cols { grid-template-columns: 1fr; }
  section.band { padding: 38px 0; }
  .overlay .panel h3 { font-size: 1.25rem; }
  .big-clock { font-size: 1.7rem; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation-duration: 0.001ms !important; animation-iteration-count: 1 !important; transition-duration: 0.001ms !important; }
}