/* ---------------------------------------------------------------
   OB–4 assembly guide — paper / ink / clay
   --------------------------------------------------------------- */
:root{
  --paper:#F5F3ED;
  --paper-2:#FAF8F3;
  --ink:#1A1917;
  --body:#4C4941;
  --muted:#8C8679;
  --line:#E2DDD1;
  --line-2:#D5CFC1;
  --accent:#C96442;
  --accent-2:#D97757;
  --serif:"Iowan Old Style","Charter","Georgia","Times New Roman",serif;
  --sans:-apple-system,BlinkMacSystemFont,"Inter","Segoe UI",Helvetica,Arial,sans-serif;
  --mono:"SF Mono",ui-monospace,"JetBrains Mono",Menlo,monospace;
  --ease:cubic-bezier(.22,.61,.36,1);
}

*,*::before,*::after{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0;background:var(--paper);color:var(--ink);
  font-family:var(--sans);font-size:15.5px;line-height:1.7;
  -webkit-font-smoothing:antialiased;text-rendering:optimizeLegibility;
}
h1,h2,h3,h4,p,dl,dd{margin:0}
a{color:inherit;text-decoration:none}
button{font:inherit;color:inherit}
::selection{background:#F0D9CD;color:var(--ink)}

/* ------------------------------------------------------------- top bar */
.topbar{
  position:sticky;top:0;z-index:40;height:58px;
  display:flex;align-items:center;justify-content:space-between;
  padding:0 clamp(18px,3vw,38px);
  background:color-mix(in srgb,var(--paper) 88%,transparent);
  backdrop-filter:saturate(120%) blur(10px);
  border-bottom:1px solid var(--line);
}
.brand{display:flex;align-items:center;gap:10px;font-size:13px;letter-spacing:.02em}
.brand-mark{
  width:9px;height:9px;border-radius:50%;
  background:var(--accent-2);box-shadow:0 0 0 3px rgba(217,119,87,.14);
}
.brand-name{font-weight:600;letter-spacing:.04em}
.brand-slash{color:var(--line-2)}
.brand-sub{color:var(--muted);font-size:12.5px}
.topbar-right{display:flex;align-items:center;gap:22px}
.step-indicator{
  font-family:var(--mono);font-size:11px;letter-spacing:.04em;color:var(--muted);
  text-transform:lowercase;
}
.toplink{font-size:12.5px;color:var(--body);border-bottom:1px solid transparent;transition:border-color .3s}
.toplink:hover{border-color:var(--ink)}

/* ------------------------------------------------------------- layout */
.layout{
  display:grid;grid-template-columns:minmax(0,1.04fr) minmax(0,.96fr);
  align-items:start;
}
.stage{
  position:sticky;top:58px;height:calc(100vh - 58px);
  grid-column:2;grid-row:1;
  border-left:1px solid var(--line);
  background:
    radial-gradient(90% 75% at 60% 16%, #FDFCF9 0%, #F4F1E9 52%, #ECE8DE 100%);
  overflow:hidden;
}
.stage-canvas{position:relative;width:100%;height:100%}
#view{display:block;width:100%;height:100%;touch-action:none;cursor:grab}
#view:active{cursor:grabbing}
.feed{grid-column:1;grid-row:1;padding:0 clamp(22px,4.6vw,78px) 0 clamp(22px,5vw,92px)}

/* ------------------------------------------------------------- hero */
.hero{padding:clamp(48px,9vh,104px) 0 clamp(40px,6vh,64px)}
.eyebrow{
  font-size:10.5px;letter-spacing:.2em;text-transform:uppercase;
  color:var(--muted);font-weight:500;margin-bottom:18px;
}
.display{
  font-family:var(--serif);font-weight:400;
  font-size:clamp(78px,9.2vw,138px);line-height:.82;
  letter-spacing:-.045em;
}
.lede{
  margin-top:26px;max-width:42ch;font-size:clamp(16px,1.35vw,18.5px);
  line-height:1.62;color:var(--body);
}
.meta-row{
  display:grid;grid-template-columns:repeat(4,minmax(0,1fr));
  gap:14px;margin-top:38px;padding-top:20px;border-top:1px solid var(--line);
}
.meta-row .k{display:block;font-size:10px;letter-spacing:.16em;text-transform:uppercase;color:var(--muted);margin-bottom:4px}
.meta-row .v{font-size:13.5px;letter-spacing:.005em}
.hero-actions{display:flex;gap:10px;margin-top:34px;flex-wrap:wrap}
.btn{
  display:inline-flex;align-items:center;gap:10px;
  padding:12px 21px;border-radius:999px;border:1px solid var(--ink);
  background:var(--ink);color:#FAF8F3;font-size:13px;letter-spacing:.015em;
  transition:transform .35s var(--ease),background .35s,border-color .35s,color .35s;
}
.btn:hover{transform:translateY(-1px);background:#000}
.btn span{transition:transform .35s var(--ease)}
.btn:hover span{transform:translateX(3px)}
.btn-ghost{background:transparent;color:var(--ink);border-color:var(--line-2)}
.btn-ghost:hover{background:#fff;border-color:var(--ink)}
.note{
  margin-top:52px;padding:18px 20px;border-left:2px solid var(--accent-2);
  background:linear-gradient(90deg,rgba(217,119,87,.06),rgba(217,119,87,0));
}
.note p{font-size:13.5px;color:var(--body);max-width:58ch;line-height:1.65}
.note strong{color:var(--ink);font-weight:600}

/* ------------------------------------------------------------- sections */
.section{padding:clamp(56px,9vh,96px) 0 0}
.section-head{max-width:60ch}
.section-head h2{
  font-family:var(--serif);font-weight:400;
  font-size:clamp(28px,2.9vw,40px);line-height:1.12;letter-spacing:-.02em;
}
.sub{margin-top:14px;color:var(--body);font-size:15px;max-width:52ch}
.h3{
  font-family:var(--serif);font-weight:400;font-size:21px;letter-spacing:-.01em;
  margin:52px 0 14px;
}

/* ------------------------------------------------------------- filters */
.filters{display:flex;flex-wrap:wrap;gap:6px;margin:32px 0 10px}
.filter{
  border:1px solid var(--line-2);background:transparent;border-radius:999px;
  padding:6px 13px 6px 14px;font-size:12px;color:var(--body);cursor:pointer;
  display:inline-flex;gap:8px;align-items:center;transition:all .3s var(--ease);
}
.filter span{font-family:var(--mono);font-size:10.5px;color:var(--muted)}
.filter:hover{border-color:var(--ink);color:var(--ink)}
.filter.is-on{background:var(--ink);border-color:var(--ink);color:#FAF8F3}
.filter.is-on span{color:rgba(250,248,243,.55)}

/* ------------------------------------------------------------- parts list */
.parts-list{border-top:1px solid var(--line);margin-top:6px}
.group-label{
  display:flex;align-items:baseline;gap:10px;
  padding:22px 6px 8px;font-size:10px;letter-spacing:.2em;text-transform:uppercase;
  color:var(--muted);
}
.group-label::after{content:"";flex:1;height:1px;background:var(--line);transform:translateY(-3px)}
.part-row{
  display:grid;grid-template-columns:30px minmax(0,1fr) auto 84px 14px;
  gap:12px;align-items:center;width:100%;
  padding:12px 6px;border:0;border-bottom:1px solid var(--line);
  background:none;text-align:left;cursor:pointer;
  transition:background .3s var(--ease),padding .3s var(--ease);
}
.part-row:hover,.part-row.is-hot{background:linear-gradient(90deg,rgba(201,100,66,.07),rgba(201,100,66,0) 60%)}
.part-row:hover{padding-left:10px}
.part-row .idx{font-family:var(--mono);font-size:10.5px;color:var(--muted)}
.part-row .name{font-size:14.5px;letter-spacing:.002em;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.part-row .size{font-family:var(--mono);font-size:10.5px;color:var(--muted);white-space:nowrap}
.part-row .swatch{
  width:7px;height:7px;border-radius:50%;justify-self:end;
  background:#fff;border:1px solid #C4BCAA;
}
.part-row .swatch.black{background:#26241F;border-color:#26241F}
.part-row .swatch.buy{background:transparent;border:1px dashed var(--muted)}
.part-row .arrow{font-size:12px;color:var(--line-2);transition:transform .3s var(--ease),color .3s}
.part-row:hover .arrow{color:var(--accent);transform:translate(2px,-2px)}
.part-row.is-active{background:rgba(201,100,66,.08)}
.part-row.is-active .name{color:var(--accent)}

/* ------------------------------------------------------------- steps */
.steps{margin-top:40px;border-bottom:1px solid var(--line)}
.step{
  display:grid;grid-template-columns:64px minmax(0,1fr);gap:clamp(16px,2.6vw,34px);
  padding:44px 0 40px;border-top:1px solid var(--line);
  scroll-margin-top:92px;transition:opacity .5s var(--ease);
}
.step-num{
  font-family:var(--serif);font-size:42px;line-height:.9;color:#CFC7B6;
  font-variant-numeric:tabular-nums;transition:color .5s var(--ease);
}
.step.is-active .step-num{color:var(--accent)}
.step-kicker{
  font-size:10px;letter-spacing:.18em;text-transform:uppercase;color:var(--muted);
  margin-bottom:10px;
}
.step h3{
  font-family:var(--serif);font-weight:400;font-size:clamp(24px,2.3vw,31px);
  letter-spacing:-.015em;line-height:1.1;margin-bottom:12px;
}
.step .lead{font-size:16px;color:var(--ink);max-width:50ch;margin-bottom:12px;line-height:1.55}
.step .body{font-size:14.5px;color:var(--body);max-width:56ch}
.chips{display:flex;flex-wrap:wrap;gap:6px;margin:20px 0 0}
.chip-part{
  display:inline-flex;align-items:center;gap:7px;
  border:1px solid var(--line-2);border-radius:999px;padding:5px 11px 5px 10px;
  font-size:11.5px;color:var(--body);background:rgba(255,255,255,.5);cursor:pointer;
  transition:all .3s var(--ease);
}
.chip-part i{width:6px;height:6px;border-radius:50%;background:#fff;border:1px solid var(--line-2)}
.chip-part[data-color="black"] i{background:#26241F;border-color:#26241F}
.chip-part[data-color="buy"] i{background:transparent;border:1px dashed var(--muted)}
.chip-part:hover{border-color:var(--ink);background:#fff;transform:translateY(-1px)}
.tip{
  display:grid;grid-template-columns:auto minmax(0,1fr);gap:12px;
  margin-top:20px;padding:13px 15px;border-radius:10px;
  background:rgba(240,235,223,.75);border:1px solid #E8E1D1;
}
.tip .tip-k{
  font-size:9.5px;letter-spacing:.16em;text-transform:uppercase;color:var(--accent);
  padding-top:2px;white-space:nowrap;
}
.tip p{font-size:13px;color:#57514A;line-height:1.6;max-width:none}
.step-meta{
  margin-top:20px;display:flex;gap:18px;font-family:var(--mono);
  font-size:10.5px;color:var(--muted);letter-spacing:.03em;
}
.steps-end{padding:44px 0 0;display:flex;align-items:center;justify-content:space-between;gap:20px;flex-wrap:wrap}
.steps-end p{font-size:13.5px;color:var(--muted)}


/* ------------------------------------------------------------- howto / tape */
.howto{margin-top:40px}
.tapefig{
  margin:26px 0 0;padding:18px 16px 12px;border:1px solid var(--line);
  border-radius:12px;background:rgba(255,255,255,.42);
}
.tapefig-scroll{overflow-x:auto}
.tapefig svg{display:block;width:100%;height:auto;min-width:560px}
.tv-table{stroke:var(--ink);stroke-width:1.3;stroke-linecap:round}
.tv-tile{fill:#FBFAF6;stroke:var(--ink);stroke-width:1.2}
.tv-tile2{fill:#FBFAF6;stroke:var(--ink);stroke-width:1.3}
.tv-seam{stroke:var(--accent);stroke-width:1.5;stroke-dasharray:3 3;stroke-linecap:round}
.tv-tape{fill:var(--accent);fill-opacity:.92}
.tv-glue{fill:#4C4941}
.tv-drop{fill:var(--accent)}
.tv-arrow{stroke:var(--accent);stroke-width:1.2;fill:none;marker-end:url(#a1)}
.tv-lbl{font-family:var(--sans);font-size:18px;fill:var(--body)}
.tv-step{font-family:var(--sans);font-size:15px;fill:var(--muted);letter-spacing:.1em;text-transform:uppercase}
.tv-note{font-family:var(--sans);font-size:13px;fill:var(--muted)}
.tv-wick{stroke:var(--accent);stroke-width:3.5;stroke-linecap:round}
.fig-ctrl{display:flex;align-items:center;gap:18px;flex-wrap:wrap;margin-top:14px}
.th-btn{
  border:1px solid var(--line-2);background:transparent;border-radius:999px;
  padding:6px 14px;font-size:11.5px;color:var(--body);cursor:pointer;
  transition:border-color .3s var(--ease),color .3s,background .3s;
}
.th-btn:hover{border-color:var(--ink);color:var(--ink)}
.th-btn[aria-pressed="true"]{background:var(--ink);border-color:var(--ink);color:#FAF8F3}
.fig-legend{
  display:flex;align-items:center;gap:8px 20px;flex-wrap:wrap;
  font-size:11.5px;color:var(--muted);
}
.sw{display:inline-block;width:20px;height:8px;border-radius:2px;margin-right:6px;vertical-align:-1px}
.sw-tape{background:var(--accent)}
.sw-seam{height:3px;background:repeating-linear-gradient(90deg,var(--accent) 0 4px,transparent 4px 8px)}
.sw-table{height:2px;background:var(--ink)}
.th-steps{
  list-style:none;margin:22px 0 0;padding:0;
  display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:20px;
}
.th-steps li{font-size:12.5px;color:var(--body);line-height:1.62;border-top:1px solid var(--line);padding-top:11px}
.th-steps b{
  display:inline-flex;align-items:center;justify-content:center;width:18px;height:18px;
  border-radius:50%;background:var(--ink);color:#FAF8F3;font-size:10px;margin-right:8px;vertical-align:1px;
  font-weight:500;
}
.th-steps em{font-style:normal;color:var(--ink);border-bottom:1px solid var(--line-2)}
@media (max-width:980px){
  .th-steps{grid-template-columns:1fr;gap:12px}
  .tapefig svg{min-width:640px}
}

/* ------------------------------------------------------------- print */
.spec-grid{
  display:grid;grid-template-columns:repeat(3,minmax(0,1fr));
  border-top:1px solid var(--line);margin-top:34px;
}
.spec{padding:18px 4px 16px;border-bottom:1px solid var(--line)}
.spec-k{font-size:10px;letter-spacing:.16em;text-transform:uppercase;color:var(--muted);margin-bottom:5px}
.spec-v{font-family:var(--serif);font-size:20px;letter-spacing:-.01em}
.table{width:100%;border-collapse:collapse;margin-top:8px}
.table th{
  text-align:left;font-weight:500;font-size:9.5px;letter-spacing:.16em;text-transform:uppercase;
  color:var(--muted);padding:10px 4px;border-bottom:1px solid var(--line);
}
.table td{padding:11px 4px;border-bottom:1px solid var(--line);font-size:13.5px;color:var(--body)}
.table td:first-child{color:var(--ink);font-family:var(--mono);font-size:12px}
.table .num{text-align:right;font-family:var(--mono);font-size:12px}
.fineprint{margin-top:30px;font-size:12px;color:var(--muted);max-width:56ch}
code{
  font-family:var(--mono);font-size:.92em;background:rgba(0,0,0,.045);
  padding:1px 5px;border-radius:4px;
}
pre{
  font-family:var(--mono);font-size:12px;background:#26241F;color:#E9E4D8;
  padding:12px 14px;border-radius:8px;overflow:auto;
}

/* ------------------------------------------------------------- fixes */
.fixlist{list-style:none;margin:10px 0 0;padding:0;border-top:1px solid var(--line);max-width:60ch}
.fixlist li{
  position:relative;padding:11px 0 11px 22px;border-bottom:1px solid var(--line);
  font-size:13.5px;color:var(--body);line-height:1.55;
}
.fixlist li::before{
  content:"";position:absolute;left:2px;top:19px;width:7px;height:7px;border-radius:50%;
  background:transparent;border:1px solid var(--accent);
}
.fixlist strong{color:var(--ink);font-weight:600}

/* ------------------------------------------------------------- footer */
.footer{padding:80px 0 64px;margin-top:64px;border-top:1px solid var(--line)}
.footer p{font-size:12.5px;color:var(--ink)}
.footer-note{margin-top:6px;color:var(--muted);font-size:11.5px}

/* ------------------------------------------------------------- stage UI */
.stage-top{
  position:absolute;top:16px;left:16px;right:16px;
  display:flex;align-items:center;justify-content:space-between;gap:12px;
  pointer-events:none;
}
.chip{
  display:inline-flex;align-items:center;gap:9px;
  background:rgba(255,255,255,.82);backdrop-filter:blur(10px);
  border:1px solid rgba(26,25,23,.07);border-radius:999px;
  padding:7px 14px 7px 12px;font-size:11.5px;letter-spacing:.01em;color:var(--body);
  box-shadow:0 1px 2px rgba(26,25,23,.04);
  max-width:70%;white-space:nowrap;overflow:hidden;text-overflow:ellipsis;
  transition:opacity .3s;
}
.chip-dot{width:6px;height:6px;border-radius:50%;background:var(--accent-2);flex:none}
.stage-count{font-family:var(--mono);font-size:10px;color:var(--muted);letter-spacing:.05em}
.stage-progress{position:absolute;top:0;left:0;right:0;height:2px;background:transparent}
.stage-progress i{display:block;height:100%;width:0;background:var(--accent-2);transition:width .6s var(--ease)}
.stage-tools{
  position:absolute;left:16px;bottom:16px;display:flex;gap:6px;flex-wrap:wrap;
}
.tool{
  border:1px solid rgba(26,25,23,.1);background:rgba(255,255,255,.82);
  backdrop-filter:blur(10px);border-radius:999px;padding:7px 13px;
  font-size:11.5px;color:var(--body);cursor:pointer;
  transition:all .3s var(--ease);box-shadow:0 1px 2px rgba(26,25,23,.04);
}
.tool:hover{border-color:rgba(26,25,23,.3);color:var(--ink);transform:translateY(-1px)}
.tool[aria-pressed="true"]{background:var(--ink);border-color:var(--ink);color:#FAF8F3}
.tool-icon{padding:7px 10px}
.stage-hint{
  position:absolute;right:16px;bottom:20px;font-size:10px;color:var(--muted);
  letter-spacing:.02em;pointer-events:none;
}
.part-card{
  position:absolute;left:16px;bottom:64px;width:min(316px,calc(100% - 32px));
  background:rgba(255,255,255,.9);backdrop-filter:blur(14px);
  border:1px solid rgba(26,25,23,.08);border-radius:12px;padding:16px 18px 14px;
  box-shadow:0 10px 30px -18px rgba(26,25,23,.35);
  animation:cardIn .45s var(--ease) both;
}
@keyframes cardIn{from{opacity:0;transform:translateY(8px)}to{opacity:1;transform:none}}
.part-card-close{
  position:absolute;top:8px;right:8px;width:26px;height:26px;border-radius:50%;
  border:0;background:transparent;color:var(--muted);font-size:17px;line-height:1;cursor:pointer;
}
.part-card-close:hover{background:rgba(0,0,0,.05);color:var(--ink)}
.part-card-kicker{font-size:9.5px;letter-spacing:.18em;text-transform:uppercase;color:var(--accent);margin-bottom:6px}
.part-card h4{font-family:var(--serif);font-weight:400;font-size:19px;letter-spacing:-.01em;margin-bottom:8px;padding-right:20px}
.part-card-role{font-size:12.5px;color:var(--body);line-height:1.55;margin-bottom:12px}
.part-card-meta{display:grid;grid-template-columns:1fr 1fr;gap:8px 14px}
.part-card-meta div{border-top:1px solid var(--line);padding-top:6px}
.part-card-meta dt{font-size:9px;letter-spacing:.14em;text-transform:uppercase;color:var(--muted)}
.part-card-meta dd{font-family:var(--mono);font-size:11px;color:var(--ink);margin-top:2px}

.loading{
  position:absolute;inset:0;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:14px;
  background:linear-gradient(180deg,rgba(250,248,243,.9),rgba(244,241,233,.9));
  transition:opacity .6s var(--ease);z-index:3;
}
.loading.is-done{opacity:0;pointer-events:none}
.loading p{font-family:var(--mono);font-size:10.5px;letter-spacing:.14em;text-transform:uppercase;color:var(--muted)}
.loading-line{width:150px;height:2px;background:var(--line-2);overflow:hidden;border-radius:2px}
.loading-line i{display:block;width:40%;height:100%;background:var(--accent-2);animation:load 1.2s var(--ease) infinite}
@keyframes load{0%{transform:translateX(-100%)}100%{transform:translateX(320%)}}

.fatal[hidden]{display:none}
.part-card[hidden]{display:none}
.fatal{
  position:absolute;inset:0;display:flex;flex-direction:column;align-items:center;justify-content:center;
  gap:10px;padding:32px;text-align:center;background:rgba(250,248,243,.96);z-index:4;
}
.fatal h3{font-family:var(--serif);font-weight:400;font-size:22px}
.fatal p{font-size:13px;color:var(--body)}
.fatal pre{margin:6px 0}

/* ------------------------------------------------------------- responsive */
@media (max-width:1180px){
  .part-row{grid-template-columns:26px minmax(0,1fr) auto 70px 12px;gap:10px}
  .part-row .size{font-size:10px}
}
@media (max-width:980px){
  .layout{display:flex;flex-direction:column}
  .stage{
    order:-1;position:sticky;top:0;height:46vh;min-height:300px;
    grid-column:auto;border-left:0;border-bottom:1px solid var(--line);z-index:30;
  }
  .feed{padding:0 clamp(18px,5vw,40px)}
  .hero{padding-top:40px}
  .display{font-size:clamp(64px,17vw,96px)}
  .meta-row{grid-template-columns:1fr 1fr;gap:16px}
  .spec-grid{grid-template-columns:1fr 1fr}
  .stage-hint{display:none}
  .stage-tools{left:12px;bottom:12px}
  .part-card{left:12px;right:12px;bottom:58px;width:auto}
  .stage-top{top:12px;left:12px;right:12px}
  .chip{max-width:78%}
  .step{grid-template-columns:44px minmax(0,1fr);padding:36px 0 32px}
  .step-num{font-size:30px}
  .part-row{grid-template-columns:22px minmax(0,1fr) auto 12px}
  .part-row .size{display:none}
  .topbar{height:52px}
  .stage{top:52px;height:calc(46vh)}
}
@media (max-width:560px){
  .brand-sub,.brand-slash,.step-indicator{display:none}
  .part-card-meta{grid-template-columns:1fr 1fr}
  .stage{height:40vh;min-height:260px;top:52px}
}
@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{animation-duration:.001ms !important;transition-duration:.001ms !important}
}