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

:root {
  --font-body: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  --font-mono: "Cascadia Code", "SF Mono", Consolas, monospace;
  --c-bg: #fff;
  --c-text: #1a1a1a;
  --c-text-2: #555;
  --c-text-3: #777;
  --c-border: #dfdfdf;
  --c-border-light: #ededed;
  --c-surface: #f7f7f7;
  --c-hl: #ffe28a;
  --c-illo: #f9f0d8;
  --c-black: #1a1a1a;
  --c-white: #fff;
  --grid-color: rgba(0, 0, 0, .035);
  --grid-size: 32px;
  --page: min(1040px, calc(100vw - 40px));
  --text-width: 72ch;
  --radius: 12px;
}

html { scroll-behavior: smooth; }

body {
  min-width: 320px;
  color: var(--c-text);
  background: var(--c-bg);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.85;
  letter-spacing: .02em;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

a { color: inherit; }
img { display: block; max-width: 100%; }
button, summary, a { -webkit-tap-highlight-color: transparent; }

.oil-bg-grid {
  position: fixed;
  inset: 0;
  z-index: -2;
  background-image:
    linear-gradient(var(--grid-color) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid-color) 1px, transparent 1px);
  background-size: var(--grid-size) var(--grid-size);
  mask-image: radial-gradient(ellipse 82% 58% at 50% 18%, black 20%, transparent 72%);
  -webkit-mask-image: radial-gradient(ellipse 82% 58% at 50% 18%, black 20%, transparent 72%);
}

.oil-bg-gradient {
  position: fixed;
  inset: 0;
  z-index: -3;
  background: radial-gradient(ellipse 70% 36% at 50% 0%, rgba(249, 240, 216, .45), transparent);
}

.skip-link {
  position: fixed;
  top: 10px;
  left: 10px;
  z-index: 30;
  padding: 8px 12px;
  background: var(--c-black);
  color: var(--c-white);
  transform: translateY(-160%);
}

.skip-link:focus { transform: translateY(0); }

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  border-bottom: 1px solid var(--c-border-light);
  background: rgba(255, 255, 255, .95);
  backdrop-filter: blur(12px);
}

.nav {
  width: var(--page);
  min-height: 68px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: 22px;
}

.brand {
  margin-right: auto;
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  text-decoration: none;
}

.brand-dot {
  width: 11px;
  height: 11px;
  background: var(--c-hl);
  border: 1px solid var(--c-black);
  transform: rotate(8deg);
}

.nav-links { display: flex; align-items: center; gap: 22px; font-size: 14px; }
.nav-link { color: var(--c-text-2); text-decoration: none; cursor: pointer; }
.nav-link:hover, .nav-link:focus-visible { color: var(--c-text); text-decoration: underline; text-underline-offset: 5px; }

.nav-menu { position: relative; }
.nav-menu summary {
  display: flex;
  align-items: center;
  gap: 6px;
  color: var(--c-text-2);
  list-style: none;
  cursor: pointer;
}

.nav-menu summary::-webkit-details-marker { display: none; }
.nav-menu summary::after { content: "⌄"; font-size: 15px; line-height: 1; transition: transform 160ms ease; }
.nav-menu[open] summary::after { transform: rotate(180deg); }

.menu-panel {
  position: absolute;
  top: calc(100% + 14px);
  right: 0;
  width: min(280px, calc(100vw - 28px));
  padding: 8px;
  border: 1px solid var(--c-black);
  border-radius: 10px;
  background: var(--c-white);
  box-shadow: 6px 6px 0 var(--c-illo);
}

.menu-panel::before {
  content: "";
  position: absolute;
  top: -15px;
  right: 0;
  width: 84px;
  height: 15px;
}

.menu-panel a {
  padding: 9px 11px;
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
  border-radius: 7px;
  color: var(--c-text);
  text-decoration: none;
  cursor: pointer;
}

.menu-panel a:hover, .menu-panel a:focus-visible { background: var(--c-surface); }
.menu-panel small { color: var(--c-text-3); font-size: 14px; }

.oil-page { width: var(--page); margin: 0 auto; }
.oil-section { padding: 68px 0; }
.oil-section + .oil-section { border-top: 1px solid var(--c-border); }

.oil-h1, .oil-h2, .oil-h3 { line-height: 1.35; letter-spacing: -.025em; text-wrap: balance; }
.oil-h1 { max-width: 11em; margin-bottom: 24px; font-size: clamp(42px, 6vw, 68px); font-weight: 700; }
.oil-h2 { margin-bottom: 18px; font-size: clamp(30px, 4vw, 42px); font-weight: 650; }
.oil-h3 { margin-bottom: 10px; font-size: 20px; font-weight: 650; }
.oil-body { max-width: var(--text-width); color: var(--c-text-2); font-size: 16px; line-height: 1.85; }
.oil-body + .oil-body { margin-top: 14px; }
.oil-caption { color: var(--c-text-3); font-size: 14px; line-height: 1.7; }
.oil-hl { padding: 0 2px; background: linear-gradient(transparent 58%, var(--c-hl) 58%, var(--c-hl) 94%, transparent 94%); }

.section-label { margin-bottom: 16px; display: inline-flex; align-items: center; gap: 10px; font-size: 14px; font-weight: 650; }
.section-label::before { content: ""; width: 28px; height: 2px; background: var(--c-black); }
.section-head { margin-bottom: 32px; display: grid; grid-template-columns: minmax(260px, .75fr) minmax(0, 1.25fr); gap: 48px; align-items: end; }
.section-head .oil-h2 { margin: 0; }

.button-row { margin-top: 28px; display: flex; flex-wrap: wrap; gap: 12px; }
.button {
  min-height: 44px;
  padding: 8px 17px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  border: 1px solid var(--c-border);
  border-radius: 999px;
  background: var(--c-white);
  font-size: 14px;
  font-weight: 650;
  text-decoration: none;
  cursor: pointer;
  transition: transform 180ms ease, border-color 180ms ease, background-color 180ms ease;
}

.button:hover { transform: translateY(-2px); border-color: var(--c-black); }
.button-primary { border-color: var(--c-black); background: var(--c-black); color: var(--c-white); }
.button-primary:hover { background: #333; }
.button-related { border-color: #d3a91e; background: var(--c-hl); color: var(--c-text); }
.button-related:hover { border-color: #9e7900; background: #f6d56d; }

.hero {
  min-height: 620px;
  padding-top: 62px;
  display: grid;
  grid-template-columns: minmax(0, 1.1fr) minmax(320px, .9fr);
  gap: clamp(48px, 8vw, 94px);
  align-items: center;
}

.hero-copy > .oil-body { max-width: 35em; font-size: 17px; }
.download-sheet { padding: 28px; border: 1px solid var(--c-black); border-radius: var(--radius); background: var(--c-white); box-shadow: 10px 10px 0 var(--c-illo); }
.download-sheet-head { display: flex; align-items: flex-start; justify-content: space-between; gap: 20px; }
.download-kicker { margin-bottom: 5px; color: var(--c-text-3); font-size: 14px; }
.download-sheet h2 { font-size: 24px; line-height: 1.35; }
.download-live { display: inline-flex; align-items: center; gap: 7px; color: var(--c-text-2); font-size: 13px; white-space: nowrap; }
.download-live::before { content: ""; width: 8px; height: 8px; border-radius: 50%; background: #d69d00; }
.download-live[data-state="ready"]::before { background: #16805d; }
.download-live[data-state="error"]::before { background: #b42318; }
.download-metric { min-height: 176px; display: flex; align-items: center; gap: 12px; }
.download-metric strong { font-family: var(--font-mono); font-size: clamp(72px, 9vw, 108px); font-weight: 650; line-height: 1; letter-spacing: -.07em; }
.download-metric span { max-width: 7em; color: var(--c-text-2); font-size: 14px; line-height: 1.5; }
.download-sheet-foot { padding-top: 18px; border-top: 1px solid var(--c-border); }
.download-sheet-foot p { color: var(--c-text-3); font-size: 13px; line-height: 1.65; }
.download-sheet-foot a { margin-top: 8px; display: inline-block; font-size: 14px; font-weight: 650; text-underline-offset: 4px; cursor: pointer; }
.download-sheet-foot a:hover { text-decoration-thickness: 2px; }

.product-demo { display: grid; grid-template-columns: minmax(0, 1.35fr) minmax(270px, .65fr); border: 1px solid var(--c-black); border-radius: var(--radius); overflow: hidden; background: var(--c-white); }
.product-screen { min-width: 0; padding: 14px; border-right: 1px solid var(--c-black); background: var(--c-surface); }
.window-bar { height: 34px; padding: 0 10px; display: flex; align-items: center; gap: 7px; border: 1px solid var(--c-border); border-bottom: 0; border-radius: 8px 8px 0 0; background: var(--c-white); }
.window-bar i { width: 9px; height: 9px; display: block; border-radius: 50%; background: #bbb; }
.window-bar span { margin-left: 8px; color: var(--c-text-3); font-size: 14px; }
.product-screen img,
.product-screen video { display: block; width: 100%; aspect-ratio: 16 / 8.5; object-fit: cover; object-position: left top; border: 1px solid var(--c-border); background: var(--c-white); }
.product-info { padding: 30px; display: flex; flex-direction: column; justify-content: space-between; }
.fact-list { margin-top: 24px; border-top: 1px solid var(--c-border); }
.fact-row { padding: 10px 0; display: flex; justify-content: space-between; gap: 18px; border-bottom: 1px solid var(--c-border); font-size: 14px; }
.fact-row span { color: var(--c-text-3); }

.flow { margin-top: 26px; display: grid; grid-template-columns: repeat(5, minmax(0, 1fr)); border-top: 1px solid var(--c-black); border-bottom: 1px solid var(--c-black); }
.flow-step { min-width: 0; padding: 18px 16px; }
.flow-step + .flow-step { border-left: 1px solid var(--c-border); }
.flow-step span { display: block; margin-bottom: 6px; font-family: var(--font-mono); font-size: 14px; }
.flow-step strong { font-size: 14px; }

.demo-showcase { padding: 68px 0; }
.demo-item + .demo-item { margin-top: 68px; padding-top: 68px; border-top: 1px solid var(--c-border); }
.demo-copy { margin-bottom: 22px; display: grid; grid-template-columns: minmax(240px, .7fr) minmax(0, 1.3fr); gap: 54px; align-items: end; }
.demo-copy .oil-h2 { margin: 0; }
.demo-frame { overflow: hidden; border: 1px solid var(--c-black); border-radius: var(--radius); background: var(--c-black); }
.demo-frame video { display: block; width: 100%; aspect-ratio: 16 / 9; background: var(--c-black); object-fit: contain; }

.oil-status { display: inline-flex; align-items: center; gap: 7px; color: var(--c-text-2); font-size: 14px; font-weight: 600; white-space: nowrap; }
.oil-status::before { content: ""; width: 8px; height: 8px; border-radius: 50%; background: #d69d00; }

.writing { display: grid; grid-template-columns: minmax(250px, .65fr) minmax(0, 1.35fr); gap: 54px; align-items: start; }
.article-list { border-top: 1px solid var(--c-black); }
.article-entry { padding: 22px 0; display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 16px; align-items: center; border-bottom: 1px solid var(--c-border); color: inherit; text-decoration: none; }
.article-entry h3 { margin: 0 0 4px; font-size: 18px; }
.article-link { color: var(--c-text-2); font-size: 14px; font-weight: 650; white-space: nowrap; }
.oil-tag { padding: 4px 10px; border-radius: 999px; background: var(--c-illo); color: #64551f; font-size: 14px; font-weight: 600; white-space: nowrap; }
.contact-card { margin-top: 28px; padding: 20px 22px; display: flex; flex-wrap: wrap; gap: 10px 22px; border: 1px solid var(--c-black); border-radius: var(--radius); font-size: 14px; }
.contact-card span, .contact-card a { color: var(--c-text-2); }
.contact-card a { text-underline-offset: 4px; cursor: pointer; }
.contact-card a:hover { color: var(--c-text); text-decoration-thickness: 2px; }

.page-hero { padding: 86px 0 56px; border-bottom: 1px solid var(--c-black); }
.page-hero .oil-h1 { max-width: 12em; }
.page-hero .oil-h1.system-design-title { width: min(12.13em, 100%); max-width: none; }
.oil-h1.collaboration-title { max-width: none; font-size: clamp(30px, 3.9vw, 48px); line-height: 1.45; text-wrap: wrap; }
.collaboration-title span { display: block; }
.page-hero .oil-body { max-width: 58em; font-size: 17px; }
.page-meta { margin-top: 28px; display: flex; flex-wrap: wrap; gap: 8px; }
.page-meta span { padding: 4px 10px; border-radius: 999px; background: var(--c-surface); color: var(--c-text-2); font-size: 14px; }

.article-hero { padding: 86px 0 64px; border-bottom: 1px solid var(--c-black); }
.article-hero .oil-h1 { max-width: 18em; margin-bottom: 0; font-size: clamp(40px, 5.3vw, 64px); }
.article-body { width: min(760px, 100%); margin: 0 auto; padding: 72px 0 96px; }
.article-body h2 { margin: 72px 0 22px; font-size: clamp(26px, 3.2vw, 36px); line-height: 1.4; letter-spacing: -.02em; text-wrap: balance; }
.article-body h2:first-child { margin-top: 0; }
.article-body p { color: #343434; font-size: 17px; line-height: 2; }
.article-body p + p { margin-top: 22px; }
.article-note { padding: 30px 0; display: grid; grid-template-columns: 54px minmax(0, 1fr); gap: 24px; border-bottom: 1px solid var(--c-border); }
.article-note:first-child { padding-top: 0; }
.article-note-id { width: 42px; height: 42px; display: grid; place-items: center; border-radius: 50%; background: var(--c-black); color: var(--c-white); font-family: var(--font-mono); font-size: 13px; }
.article-note-title { margin: 0 0 10px; font-size: 20px; line-height: 1.45; letter-spacing: -.01em; }
.article-note p { margin: 0; }

.two-col { display: grid; grid-template-columns: minmax(240px, .7fr) minmax(0, 1.3fr); gap: 54px; align-items: start; }
.three-col { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); border-top: 1px solid var(--c-black); }
.column-item { min-width: 0; padding: 24px 26px 0 0; }
.column-item + .column-item { padding-left: 26px; border-left: 1px solid var(--c-border); }
.column-item p { color: var(--c-text-2); font-size: 15px; }

.plain-list { list-style: none; border-top: 1px solid var(--c-black); }
.plain-list li { padding: 16px 0; display: grid; grid-template-columns: minmax(160px, .45fr) minmax(0, 1.55fr); gap: 24px; border-bottom: 1px solid var(--c-border); }
.plain-list p { color: var(--c-text-2); }

.callout { padding: 22px 24px; border-radius: var(--radius); background: var(--c-illo); }
.callout p { color: #454035; }
.comparison-panel { background: var(--c-white); }
.comparison-row + .comparison-row { margin-top: 40px; padding-top: 40px; border-top: 1px solid var(--c-border); }
.solution-list { padding-left: 1.2em; color: #454035; }
.solution-list li + li { margin-top: 9px; }

.decision-list { border-top: 1px solid var(--c-black); }
.decision { padding: 28px 0; display: grid; grid-template-columns: 90px minmax(0, 1fr); gap: 26px; border-bottom: 1px solid var(--c-border); }
.decision-id { width: 48px; height: 48px; display: grid; place-items: center; border-radius: 50%; background: var(--c-black); color: var(--c-white); font-family: var(--font-mono); font-size: 14px; }
.decision-copy { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: 28px; }
.decision-copy p { color: var(--c-text-2); font-size: 15px; }
.decision-copy strong { display: block; margin-bottom: 4px; color: var(--c-text); }

.evidence-table { width: 100%; border-collapse: collapse; border-top: 1px solid var(--c-black); }
.evidence-table th, .evidence-table td { padding: 15px 14px; border-bottom: 1px solid var(--c-border); text-align: left; vertical-align: top; }
.evidence-table th { width: 22%; font-size: 14px; }
.evidence-table td { color: var(--c-text-2); font-size: 14px; }

.role-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); border: 1px solid var(--c-black); border-radius: var(--radius); overflow: hidden; }
.role-grid-two { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.role { padding: 26px; background: var(--c-white); }
.role + .role { border-left: 1px solid var(--c-border); }
.role-note { margin-bottom: 14px; color: var(--c-text-2); font-size: 14px; }
.role ul { padding-left: 1.15em; color: var(--c-text-2); font-size: 14px; }
.role li + li { margin-top: 7px; }

footer { width: var(--page); margin: 0 auto; padding: 26px 0 42px; display: flex; justify-content: space-between; gap: 20px; border-top: 1px solid var(--c-border); color: var(--c-text-3); font-size: 14px; }

:focus-visible { outline: 3px solid #d69d00; outline-offset: 3px; }

@media (hover: hover) and (pointer: fine) {
  .nav-menu:not([open]):hover .menu-panel { display: block; }
  .article-entry:hover { background: linear-gradient(90deg, rgba(249, 240, 216, .72), transparent 82%); }
  .article-entry:hover .article-link { color: var(--c-text); }
}

@media (max-width: 820px) {
  .hero { min-height: auto; grid-template-columns: 1fr; padding-top: 68px; }
  .section-head, .product-demo, .writing, .two-col, .demo-copy { grid-template-columns: 1fr; }
  .section-head { gap: 16px; }
  .demo-copy { gap: 8px; }
  .product-screen { border-right: 0; border-bottom: 1px solid var(--c-black); }
  .flow { grid-template-columns: 1fr 1fr; }
  .flow-step:nth-child(odd) { border-left: 0; }
  .flow-step:nth-child(n + 3) { border-top: 1px solid var(--c-border); }
  .three-col, .role-grid { grid-template-columns: 1fr; }
  .column-item { padding: 22px 0; }
  .column-item + .column-item { padding-left: 0; border-top: 1px solid var(--c-border); border-left: 0; }
  .role + .role { border-top: 1px solid var(--c-border); border-left: 0; }
}

@media (max-width: 600px) {
  :root { --page: calc(100vw - 28px); }
  .nav { min-height: 62px; gap: 14px; }
  .nav-links { gap: 14px; }
  .nav-links > .nav-link:not(.resume-link) { display: none; }
  .oil-section { padding: 60px 0; }
  .oil-h1 { font-size: clamp(38px, 12vw, 52px); }
  .download-sheet { padding: 22px; box-shadow: 7px 7px 0 var(--c-illo); }
  .download-metric { min-height: 150px; }
  .writing { gap: 28px; }
  .article-hero { padding-top: 66px; }
  .article-body { padding: 54px 0 72px; }
  .article-body h2 { margin-top: 54px; }
  .article-note { grid-template-columns: 42px minmax(0, 1fr); gap: 16px; }
  .page-hero { padding-top: 66px; }
  .plain-list li { grid-template-columns: 1fr; gap: 4px; }
  .decision { grid-template-columns: 48px minmax(0, 1fr); gap: 16px; }
  .decision-copy { grid-template-columns: 1fr; gap: 12px; }
  .evidence-table { display: block; overflow-x: auto; }
  footer { display: block; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { transition-duration: .01ms !important; }
  .button:hover { transform: none; }
}