/* ==========================================================================
   Survey — gedik.tech design system. Spec: /DESIGN.md
   ========================================================================== */

/* ---------- Tokens ---------- */
:root {
  --paper: #F1EEE6;
  --paper-2: #E9E5DA;
  --ink: #151513;
  --ink-2: #4A4943;
  --ink-3: #7A776D;
  --rule: rgba(21, 21, 19, .14);
  --rule-strong: #151513;
  --signal: #C2410C;
  --signal-wash: rgba(194, 65, 12, .10);
  --topo-line: rgba(21, 21, 19, .18);
  --topo-index: rgba(194, 65, 12, .55);

  --f-display: 'Instrument Serif', 'Times New Roman', serif;
  --f-text: 'IBM Plex Sans', system-ui, -apple-system, sans-serif;
  --f-mono: 'IBM Plex Mono', ui-monospace, 'SFMono-Regular', Menlo, monospace;

  --fs-hero: clamp(4.5rem, 15vw, 14rem);
  --fs-h2: clamp(2.4rem, 5vw, 4rem);
  --fs-h3: clamp(1.6rem, 2.6vw, 2.1rem);
  --fs-lede: clamp(1.1rem, 1.5vw, 1.3rem);
  --fs-body: 1rem;
  --fs-small: .875rem;
  --fs-meta: .72rem;

  --s-1: 4px; --s-2: 8px; --s-3: 12px; --s-4: 16px; --s-5: 24px;
  --s-6: 32px; --s-7: 48px; --s-8: 72px; --s-9: 120px;

  --wrap: 1320px;
  --gutter: clamp(20px, 4vw, 48px);
  --radius: 2px;
  --bar-h: 56px;
  --ease: cubic-bezier(.2, .7, .2, 1);

  color-scheme: light;
}

[data-theme="dark"] {
  --paper: #121310;
  --paper-2: #181A16;
  --ink: #ECE8DD;
  --ink-2: #B4B0A5;
  --ink-3: #85827A;
  --rule: rgba(236, 232, 221, .14);
  --rule-strong: #ECE8DD;
  --signal: #FF7A3D;
  --signal-wash: rgba(255, 122, 61, .14);
  --topo-line: rgba(236, 232, 221, .14);
  --topo-index: rgba(255, 122, 61, .5);
  color-scheme: dark;
}

/* ---------- Base ---------- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 17px; scroll-behavior: smooth; scroll-padding-top: calc(var(--bar-h) + 16px); -webkit-text-size-adjust: 100%; }
body {
  background: var(--paper);
  color: var(--ink);
  font-family: var(--f-text);
  font-size: var(--fs-body);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  transition: background-color .25s var(--ease), color .25s var(--ease);
}
img, svg { display: block; max-width: 100%; }
a { color: inherit; }
b, strong { font-weight: 600; }
::selection { background: var(--signal); color: var(--paper); }
:focus-visible { outline: 2px solid var(--signal); outline-offset: 3px; }

.wrap { max-width: var(--wrap); margin: 0 auto; padding: 0 var(--gutter); }
.sr-only { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }

/* ---------- Type primitives ---------- */
.display { font-family: var(--f-display); font-weight: 400; letter-spacing: -.01em; }
.display em, h1 em, h2 em, h3 em { font-style: italic; }
.meta {
  font-family: var(--f-mono);
  font-size: var(--fs-meta);
  font-weight: 400;
  letter-spacing: .06em;
  text-transform: uppercase;
  color: var(--ink-3);
  line-height: 1.4;
}
.meta b { font-weight: 500; color: var(--ink); }
.lede { font-size: var(--fs-lede); line-height: 1.5; color: var(--ink-2); max-width: 44ch; }
.lede b { color: var(--ink); font-weight: 500; }
.prose p { max-width: 68ch; color: var(--ink-2); }
.prose p + p { margin-top: var(--s-4); }
.prose b { color: var(--ink); }
.prose a, a.u { text-decoration: underline; text-decoration-thickness: 1px; text-underline-offset: 3px; text-decoration-color: var(--rule-strong); }
.prose a:hover, a.u:hover { text-decoration-color: var(--signal); }
.signal { color: var(--signal); }

/* ---------- Top bar ---------- */
.bar {
  position: fixed; inset: 0 0 auto 0; z-index: 50;
  height: var(--bar-h);
  background: var(--paper);
  border-bottom: 1px solid var(--rule);
  transition: background-color .25s var(--ease);
}
.bar-inner { height: 100%; display: flex; align-items: center; gap: var(--s-6); }
.mark {
  font-family: var(--f-mono); font-size: .8rem; font-weight: 500;
  letter-spacing: .04em; text-decoration: none; white-space: nowrap;
  display: inline-flex; align-items: center; gap: var(--s-2);
}
.mark::before { content: ""; width: 9px; height: 9px; background: var(--signal); }
.mark span { color: var(--ink-3); font-weight: 400; }
.nav { display: flex; gap: var(--s-5); margin-left: auto; }
.nav a {
  font-family: var(--f-mono); font-size: var(--fs-meta); letter-spacing: .06em; text-transform: uppercase;
  text-decoration: none; color: var(--ink-2); padding: var(--s-1) 0; position: relative;
  transition: color .15s var(--ease);
}
.nav a:hover { color: var(--ink); }
.nav a.active { color: var(--ink); }
.nav a.active::before { content: "■"; color: var(--signal); font-size: .6em; position: absolute; left: -12px; top: 50%; transform: translateY(-50%); }
.nav a.ext { color: var(--ink); }
.bar-tools { display: flex; align-items: center; gap: var(--s-4); }
.clock { white-space: nowrap; }
.toggle {
  font-family: var(--f-mono); font-size: var(--fs-meta); letter-spacing: .06em; text-transform: uppercase;
  background: none; border: 1px solid var(--rule); color: var(--ink); cursor: pointer;
  height: 30px; padding: 0 var(--s-3); border-radius: var(--radius);
  transition: border-color .15s var(--ease);
}
.toggle:hover { border-color: var(--ink); }
.menu-btn { display: none; }

.drawer {
  position: fixed; inset: var(--bar-h) 0 auto 0; z-index: 49;
  background: var(--paper); border-bottom: 1px solid var(--rule-strong);
  display: none; flex-direction: column; padding: var(--s-3) var(--gutter) var(--s-5);
}
.drawer.open { display: flex; }
.drawer a {
  font-family: var(--f-display); font-size: 2rem; text-decoration: none;
  padding: var(--s-2) 0; border-bottom: 1px solid var(--rule);
  display: flex; justify-content: space-between; align-items: baseline;
}
.drawer a span { font-family: var(--f-mono); font-size: var(--fs-meta); color: var(--signal); }

/* ---------- Sections ---------- */
.sec { padding: var(--s-9) 0; }
.sec--band { background: var(--paper-2); }
.sec-grid { display: grid; grid-template-columns: repeat(12, minmax(0, 1fr)); gap: var(--s-5); border-top: 1px solid var(--rule-strong); padding-top: var(--s-5); }
.wrap.sec-grid { border-top: 0; position: relative; }
.wrap.sec-grid::before { content: ""; position: absolute; top: 0; left: var(--gutter); right: var(--gutter); border-top: 1px solid var(--rule-strong); }
.sec-rail { grid-column: 1 / span 4; }
.sec-body { grid-column: 5 / span 8; }
.sec-no { font-family: var(--f-mono); font-size: var(--fs-meta); letter-spacing: .06em; color: var(--signal); display: block; margin-bottom: var(--s-3); }
.sec-title { font-family: var(--f-display); font-weight: 400; font-size: var(--fs-h2); line-height: 1; letter-spacing: -.015em; }
.sec-note { margin-top: var(--s-4); max-width: 30ch; }
.sec-rail.sticky { position: sticky; top: calc(var(--bar-h) + var(--s-5)); align-self: start; }

/* ---------- Buttons, tags ---------- */
.btn {
  display: inline-flex; align-items: center; gap: var(--s-3);
  height: 46px; padding: 0 var(--s-5);
  font-family: var(--f-mono); font-size: .78rem; font-weight: 500; letter-spacing: .06em; text-transform: uppercase;
  text-decoration: none; border-radius: var(--radius); border: 1px solid var(--ink);
  transition: background-color .15s var(--ease), color .15s var(--ease), border-color .15s var(--ease);
}
.btn--ink { background: var(--ink); color: var(--paper); }
.btn--ink:hover { background: var(--signal); border-color: var(--signal); color: #fff; }
.btn--line { background: transparent; color: var(--ink); border-color: var(--rule); }
.btn--line:hover { border-color: var(--ink); }
.btn .arr { transition: transform .15s var(--ease); }
.btn:hover .arr { transform: translate(2px, -2px); }
.btn:hover .arr--r { transform: translateX(3px); }

.tag {
  font-family: var(--f-mono); font-size: var(--fs-meta); letter-spacing: .06em; text-transform: uppercase;
  color: var(--ink-2); display: inline-flex; align-items: center; gap: var(--s-2);
}
.tag::before { content: "■"; color: var(--signal); font-size: .75em; }

.links { display: flex; flex-wrap: wrap; gap: var(--s-2) var(--s-5); }
.links a, .links span {
  font-family: var(--f-mono); font-size: var(--fs-meta); letter-spacing: .06em; text-transform: uppercase;
  text-decoration: none; color: var(--ink);
  border-bottom: 1px solid var(--ink); padding-bottom: 2px;
  transition: color .15s var(--ease), border-color .15s var(--ease);
}
.links a:hover { color: var(--signal); border-color: var(--signal); }
.links span { color: var(--ink-3); border-bottom-style: dotted; border-color: var(--ink-3); }

/* ---------- Spec table ---------- */
.spec { width: 100%; border-collapse: collapse; }
.spec div { display: grid; grid-template-columns: 11ch 1fr; gap: var(--s-4); padding: var(--s-2) 0; border-bottom: 1px solid var(--rule); }
.spec div:first-child { border-top: 1px solid var(--rule); }
.spec dt { font-family: var(--f-mono); font-size: var(--fs-meta); letter-spacing: .06em; text-transform: uppercase; color: var(--ink-3); padding-top: 3px; }
.spec dd { font-size: var(--fs-small); color: var(--ink); line-height: 1.5; }

/* ---------- Stats ---------- */
.stats { display: grid; grid-template-columns: 1fr 1fr; border-top: 1px solid var(--rule); }
.stat { padding: var(--s-5) 0 var(--s-4); border-bottom: 1px solid var(--rule); }
.stat:nth-child(odd) { padding-right: var(--s-4); border-right: 1px solid var(--rule); }
.stat:nth-child(even) { padding-left: var(--s-5); }
.stat .n { font-family: var(--f-display); font-size: clamp(3rem, 5vw, 4.25rem); line-height: .9; letter-spacing: -.02em; }
.stat .n sup { font-size: .4em; color: var(--signal); vertical-align: top; position: relative; top: .35em; margin-left: 2px; }
.stat .meta { margin-top: var(--s-3); }

/* ---------- Figures ---------- */
.fig { position: relative; }
.fig-frame { border: 1px solid var(--rule-strong); background: var(--paper-2); overflow: hidden; display: block; }
.fig-frame img { width: 100%; height: 100%; object-fit: cover; transition: transform .6s var(--ease); }
a.fig-frame:hover img { transform: scale(1.02); }
.fig figcaption { margin-top: var(--s-3); display: flex; justify-content: space-between; gap: var(--s-4); }
.fig figcaption .meta + .meta { white-space: nowrap; }
.fig figcaption .meta:first-child b { color: var(--signal); font-weight: 500; }

/* ---------- Case study ---------- */
.case { display: grid; grid-template-columns: repeat(12, minmax(0, 1fr)); gap: var(--s-5); padding: var(--s-7) 0; border-bottom: 1px solid var(--rule); }
.case-head { grid-column: 1 / -1; display: grid; grid-template-columns: subgrid; align-items: baseline; }
.case-no { grid-column: 1 / span 3; font-family: var(--f-mono); font-size: var(--fs-meta); color: var(--signal); letter-spacing: .06em; }
.case h3 { grid-column: 4 / -1; font-family: var(--f-display); font-weight: 400; font-size: var(--fs-h3); line-height: 1.1; letter-spacing: -.01em; max-width: 28ch; }
.case-meta { grid-column: 1 / span 3; align-self: start; }
.case-text { grid-column: 4 / span 5; }
.case-fig { grid-column: 9 / -1; align-self: start; }
.case--wide .case-fig { grid-column: 4 / -1; margin-top: var(--s-3); }
.case-meta .spec div { grid-template-columns: 1fr; gap: 2px; }
.case-meta .links { margin-top: var(--s-5); }

.callout {
  margin-top: var(--s-5); padding: var(--s-4) var(--s-5);
  background: var(--signal-wash); border-left: 2px solid var(--signal);
  font-size: var(--fs-small); color: var(--ink); max-width: 68ch;
}
.callout .meta { display: block; color: var(--signal); margin-bottom: var(--s-1); }

/* ---------- Ledger ---------- */
.ledger { border-top: 1px solid var(--rule-strong); }
.ledger-head, .ledger-row { display: grid; grid-template-columns: 3.5ch minmax(0, 4fr) minmax(0, 7fr); gap: var(--s-5); }
.ledger-head { padding: var(--s-2) 0; border-bottom: 1px solid var(--rule); }
.ledger-row { padding: var(--s-5) 0; border-bottom: 1px solid var(--rule); transition: background-color .15s var(--ease); }
.ledger-row .no { font-family: var(--f-mono); font-size: var(--fs-meta); color: var(--ink-3); padding-top: 6px; }
.ledger-row h4 { font-family: var(--f-display); font-weight: 400; font-size: 1.55rem; line-height: 1.15; letter-spacing: -.005em; }
.ledger-row .tag { margin-top: var(--s-2); }
.ledger-row p { color: var(--ink-2); font-size: var(--fs-small); max-width: 62ch; }
.ledger-row p.stack { margin-top: var(--s-3); font-size: var(--fs-meta); color: var(--ink-3); }
.ledger-row .links { margin-top: var(--s-3); }
.ledger-row .when { font-family: var(--f-mono); font-size: var(--fs-meta); letter-spacing: .06em; text-transform: uppercase; color: var(--ink-3); display: block; margin-top: var(--s-2); }

/* ---------- Columns list ---------- */
.cols { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: var(--s-5); }
.cols h3 { font-family: var(--f-mono); font-size: var(--fs-meta); font-weight: 500; letter-spacing: .06em; text-transform: uppercase; color: var(--signal); padding-bottom: var(--s-3); border-bottom: 1px solid var(--rule-strong); }
.cols ul { list-style: none; }
.cols li { padding: var(--s-3) 0; border-bottom: 1px solid var(--rule); color: var(--ink-2); font-size: var(--fs-small); }

/* ---------- Topo backdrop ---------- */
.topo { position: absolute; inset: 0; pointer-events: none; overflow: hidden;
  -webkit-mask-image: linear-gradient(90deg, transparent 0%, transparent 28%, #000 62%);
          mask-image: linear-gradient(90deg, transparent 0%, transparent 28%, #000 62%); }
.topo svg { width: 100%; height: 100%; }
.topo path { fill: none; stroke: var(--topo-line); stroke-width: .22; }
.topo path.ci { stroke: var(--topo-index); stroke-width: .38; }
@media (prefers-reduced-motion: no-preference) {
  .topo.draw path { stroke-dasharray: 1; stroke-dashoffset: 1; animation: topo-draw 2.8s var(--ease) forwards; }
  .topo.draw path.ci { animation-duration: 3.4s; animation-delay: .3s; }
}
@keyframes topo-draw { to { stroke-dashoffset: 0; } }

/* ---------- Footer ---------- */
.foot { border-top: 1px solid var(--rule-strong); padding: var(--s-5) 0 var(--s-7); }
.foot-inner { display: flex; justify-content: space-between; align-items: baseline; gap: var(--s-5); flex-wrap: wrap; }

/* ---------- Responsive ---------- */
@media (max-width: 1080px) {
  .nav { gap: var(--s-4); }
  .clock { display: none; }
}
@media (max-width: 900px) {
  :root { --bar-h: 52px; }
  .nav { display: none; }
  .menu-btn { display: inline-flex; align-items: center; }
  .mark span { display: none; }
  .bar-tools { margin-left: auto; }
  .sec { padding: var(--s-8) 0; }
  .sec-grid { gap: var(--s-5) 0; }
  .sec-rail, .sec-body { grid-column: 1 / -1; }
  .sec-rail.sticky { position: static; }
  .case { grid-template-columns: 1fr; gap: var(--s-4); }
  .case-head { display: block; }
  .case-no { display: block; margin-bottom: var(--s-2); }
  .case-meta, .case-text, .case-fig, .case--wide .case-fig { grid-column: 1 / -1; }
  .case-text { order: 1; }
  .case-fig { order: 2; margin-top: var(--s-2); }
  .case-meta { order: 3; }
  .ledger-head { display: none; }
  .ledger-row { grid-template-columns: 3.5ch minmax(0, 1fr); gap: var(--s-3) var(--s-4); }
  .ledger-row > :last-child { grid-column: 2; }
  .cols { grid-template-columns: 1fr; gap: var(--s-6); }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { transition: none !important; animation: none !important; }
}