/* Swiss tokens + systematic metrics for relativity-observatory (P0).
   Anchor: Swiss — white surface, single accent, hairline grid, sans + tabular numerals.
   All design math lives here; view code uses variables and named classes. */
:root {
  --surface: #ffffff;
  --surface-alt: #f7f7f8;
  --ink: #111111;
  --muted: #555555;
  --line: #e2e2e4;
  --line-strong: #111111;
  --accent: #002fa7;
  --accent-pressed: #001f70;
  --accent-soft: #e8edfb;
  --focus: #002fa7;
  --max-width: 1120px;
  --inset: 20px;
  --section-gap: 28px;
  --card-pad: 20px;
  --radius: 2px;
  --font: "Helvetica Neue", helvetica, "Apple SD Gothic Neo", "Noto Sans KR", system-ui, -apple-system, sans-serif;
  --mono-nums: tabular-nums;
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--surface);
  color: var(--ink);
  font-family: var(--font);
  line-height: 1.6;
  font-size: 16px;
}
.num, td, th, output, input { font-variant-numeric: var(--mono-nums); }

/* Landmarks */
.skip-link {
  position: absolute; left: 12px; top: -48px; z-index: 50;
  background: var(--ink); color: #fff; padding: 10px 14px; border-radius: var(--radius);
  transition: top 0.15s ease;
}
.skip-link:focus { top: 12px; color: #fff; }
.site-header {
  border-bottom: 1px solid var(--line);
  background: var(--surface);
}
.site-header-inner {
  max-width: var(--max-width); margin: 0 auto; padding: 14px var(--inset);
  display: flex; align-items: center; gap: 16px; justify-content: space-between;
}
.brand { display: flex; align-items: baseline; gap: 12px; }
.brand-folio { font-size: 12px; letter-spacing: 0.08em; color: var(--muted); }
h1 { font-size: 22px; margin: 0; letter-spacing: -0.01em; }
main { max-width: var(--max-width); margin: 0 auto; padding: 24px var(--inset) 64px; }
.page-lead { border-left: 4px solid var(--accent); padding-left: 14px; margin: 0 0 24px; }
.page-lead p { margin: 6px 0; }
.muted { color: var(--muted); }
/* 도입 삽화: 계산 화면과 분리된 맥락 제공용. 수치는 표·도표가 담당. */
.intro-strip {
  display: grid; gap: 12px; margin: 16px 0 0;
  grid-template-columns: repeat(3, minmax(0, 1fr));
}
.intro-strip picture { border: 1px solid var(--line); background: #fff; }
.intro-strip img { display: block; width: 100%; height: auto; }
.intro-strip figcaption { grid-column: 1 / -1; font-size: 13px; color: var(--muted); }

/* Grid structure — min-width:0 keeps tables/fieldsets from forcing page overflow */
.layout {
  display: grid; gap: 24px;
  grid-template-columns: minmax(0, 7fr) minmax(0, 5fr);
  align-items: start;
}
.layout > * { min-width: 0; }
.stack { min-width: 0; }
@media (max-width: 900px) { .layout { grid-template-columns: minmax(0, 1fr); } }
.stack > * + * { margin-top: var(--section-gap); }

.card {
  background: var(--surface); border: 1px solid var(--line-strong);
  border-radius: var(--radius); padding: var(--card-pad);
  min-width: 0; overflow-wrap: break-word;
}
fieldset { min-inline-size: 0; }
.card-alt { background: var(--surface-alt); border-color: var(--line); }
.card h2 { font-size: 18px; margin: 0 0 4px; }
.card h3 { font-size: 15px; margin: 18px 0 8px; }
.rule { border: 0; border-top: 1px solid var(--line); margin: 16px 0; }
.grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
@media (max-width: 560px) { .grid-2 { grid-template-columns: 1fr; } }

/* Controls — one button family with variants */
.btn {
  appearance: none; border: 1px solid var(--line-strong); background: var(--surface);
  color: var(--ink); padding: 10px 16px; font-size: 15px; min-height: 44px;
  border-radius: var(--radius); cursor: pointer; font-family: inherit;
}
.btn:hover { background: var(--surface-alt); }
.btn:active { transform: translateY(1px); }
.btn-primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn-primary:hover { background: var(--accent-pressed); }
/* gi-pulse: single primary action only; static border under reduced motion */
.btn-primary.is-pulse { animation: pulse-aura 2.2s ease-out infinite; }
@keyframes pulse-aura {
  0% { box-shadow: 0 0 0 0 rgba(0, 47, 167, 0.45); }
  70% { box-shadow: 0 0 0 12px rgba(0, 47, 167, 0); }
  100% { box-shadow: 0 0 0 0 rgba(0, 47, 167, 0); }
}
@media (prefers-reduced-motion: reduce) {
  .btn-primary.is-pulse { animation: none; outline: 2px solid var(--accent); outline-offset: 2px; }
  * { scroll-behavior: auto !important; transition: none !important; }
}
.btn[disabled] { opacity: 0.55; cursor: not-allowed; }
:focus-visible { outline: 3px solid var(--focus); outline-offset: 2px; }

.field { display: grid; gap: 6px; margin: 10px 0; }
.field label { font-weight: 700; font-size: 14px; }
.field .hint { font-size: 13px; color: var(--muted); }
.field input[type="number"], .field select, .field textarea {
  font: inherit; padding: 10px 12px; border: 1px solid var(--line-strong);
  border-radius: var(--radius); background: #fff; max-width: 100%;
}
.field textarea { min-height: 96px; }
.field [aria-invalid="true"] { border-width: 2px; }
.error-text { font-size: 13px; color: var(--ink); border-left: 4px solid var(--ink); padding-left: 8px; }
.error-text::before { content: "오류: "; font-weight: 700; }
fieldset { border: 1px solid var(--line); padding: 12px; margin: 12px 0; }
legend { font-weight: 700; padding: 0 6px; }
.radio-row { display: flex; gap: 12px; flex-wrap: wrap; }
.radio-row label { display: inline-flex; gap: 8px; align-items: center; border: 1px solid var(--line); padding: 8px 12px; min-height: 44px; cursor: pointer; }
.radio-row input { width: 20px; height: 20px; accent-color: var(--accent); }

/* Tables */
.table-wrap { overflow-x: auto; border: 1px solid var(--line); max-width: 100%; }
.table-scroll-hint { display: none; font-size: 13px; margin: 4px 0 12px; }
table { border-collapse: collapse; width: 100%; min-width: 520px; font-size: 14px; }
caption { text-align: left; font-weight: 700; padding: 8px 10px; background: var(--surface-alt); }
th, td { border-top: 1px solid var(--line); padding: 8px 10px; text-align: right; }
th:first-child, td:first-child { text-align: left; }
thead th { background: var(--surface-alt); border-top: 0; }
.badge { display: inline-block; border: 1px solid var(--line-strong); padding: 1px 8px; font-size: 12px; }
.badge[data-kind="timelike"] { background: var(--ink); color: #fff; }
.badge[data-kind="lightlike"] { background: var(--accent-soft); border-style: dashed; }
.badge[data-kind="spacelike"] { background: #fff; }

/* Diagram + scene */
.figure { border: 1px solid var(--line); background: #fff; padding: 8px; }
.figure svg { display: block; width: 100%; height: auto; }
.figure figcaption { font-size: 13px; color: var(--muted); padding: 6px 2px 0; }
.status-line { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; font-size: 14px; }
.stepper { display: flex; gap: 8px; list-style: none; padding: 0; margin: 12px 0; flex-wrap: wrap; }
.stepper li { border: 1px solid var(--line); padding: 4px 10px; font-size: 13px; color: var(--muted); }
.stepper li[aria-current="step"] { border-color: var(--accent); color: var(--accent); font-weight: 700; }

input[type="range"] { width: 100%; accent-color: var(--accent); min-height: 44px; }
dialog { border: 1px solid var(--line-strong); padding: 20px; max-width: min(560px, 92vw); }
dialog::backdrop { background: rgba(0, 0, 0, 0.35); }
.record-item { border-top: 1px solid var(--line); padding: 10px 0; font-size: 14px; }
.advanced-note { border-top: 1px solid var(--line); padding-top: 10px; margin-top: 12px; }
.advanced-note summary, #advanced-details summary { cursor: pointer; font-weight: 700; }
#advanced-section[hidden], #record-section[hidden], #analysis-results[hidden] { display: none; }
@media (max-width: 600px) { .table-scroll-hint { display: block; } }
footer.site-footer { border-top: 1px solid var(--line); padding: 18px var(--inset) 40px; color: var(--muted); font-size: 13px; }
footer.site-footer .inner { max-width: var(--max-width); margin: 0 auto; }

@media (min-width: 901px) { :root { --inset: 32px; } }