:root {
  --ink: #111111;
  --paper: #ffffff;
  --wash: #f4f4f4;
  --line: #111111;
  --mute: #5a5a5a;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--paper);
  color: var(--ink);
  font-family: "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  line-height: 1.75;
  font-size: 17px;
}

img, svg { display: block; }
a { color: inherit; text-decoration: none; }
a:hover { text-decoration: underline; }

.wrap {
  width: min(1120px, calc(100% - 40px));
  margin: 0 auto;
}

.site-header {
  border-bottom: 3px solid var(--ink);
  background: var(--paper);
}
.site-header .wrap {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  min-height: 72px;
}
.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 800;
  letter-spacing: 0.02em;
  font-size: 1.05rem;
}
.brand svg { width: 28px; height: 28px; }
.nav {
  display: flex;
  flex-wrap: wrap;
  gap: 16px 22px;
  font-size: 0.92rem;
  font-weight: 600;
}

.icon-strip {
  display: flex;
  gap: 10px;
  overflow: auto;
  padding: 14px 0 4px;
}
.icon-strip span {
  flex: 0 0 auto;
  width: 52px;
  height: 52px;
  border: 2px solid var(--ink);
  display: grid;
  place-items: center;
  background: var(--paper);
}
.icon-strip svg { width: 26px; height: 26px; }

.hero {
  padding: 36px 0 20px;
  border-bottom: 3px solid var(--ink);
}
.hero h1 {
  margin: 0 0 16px;
  font-size: clamp(2.2rem, 6vw, 4rem);
  line-height: 1.08;
  letter-spacing: -0.045em;
  font-weight: 900;
  max-width: 18ch;
}
.hero p {
  margin: 0 0 12px;
  max-width: 62ch;
  font-size: 1.05rem;
}

.zoom-board {
  margin-top: 22px;
  border: 2px solid var(--ink);
  padding: 16px 18px 20px;
  background: var(--wash);
}
.zoom-board .scale-row {
  display: flex;
  align-items: center;
  gap: 14px;
  flex-wrap: wrap;
}
.zoom-board label {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-weight: 700;
  cursor: pointer;
}
.zoom-rail {
  position: relative;
  flex: 1 1 280px;
  height: 10px;
  background: repeating-linear-gradient(90deg, var(--ink) 0 2px, transparent 2px 12.5%);
  border-top: 2px solid var(--ink);
  border-bottom: 2px solid var(--ink);
}
.zoom-knob {
  position: absolute;
  top: -8px;
  width: 26px;
  height: 26px;
  border: 2px solid var(--ink);
  background: var(--paper);
}
.zoom-board:has(#z100:checked) .zoom-knob { left: 0; }
.zoom-board:has(#z125:checked) .zoom-knob { left: calc(33% - 8px); }
.zoom-board:has(#z150:checked) .zoom-knob { left: calc(66% - 14px); }
.zoom-board:has(#z175:checked) .zoom-knob { left: calc(100% - 26px); }
.sr { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); }

.bubble-stage {
  margin-top: 16px;
  display: grid;
  gap: 10px;
  max-width: 420px;
}
.bubble {
  border: 2px solid var(--ink);
  background: var(--paper);
  padding: 8px 12px 18px;
  position: relative;
  width: fit-content;
  max-width: 100%;
}
.bubble .meta {
  position: absolute;
  right: 8px;
  bottom: 2px;
  font-size: 0.72rem;
  color: var(--mute);
}
.zoom-board:has(#z100:checked) .bubble { font-size: 15px; }
.zoom-board:has(#z125:checked) .bubble { font-size: 19px; }
.zoom-board:has(#z150:checked) .bubble { font-size: 22px; }
.zoom-board:has(#z175:checked) .bubble { font-size: 26px; }

.section {
  padding: 48px 0;
  border-bottom: 1px solid #d8d8d8;
}
.section h2 {
  margin: 0 0 16px;
  font-size: clamp(1.6rem, 3vw, 2.15rem);
  line-height: 1.2;
  letter-spacing: -0.03em;
  font-weight: 900;
}
.section p { margin: 0 0 14px; }

.dense-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-top: 18px;
}
.dense-card {
  border: 2px solid var(--ink);
  padding: 16px 18px;
  background: var(--paper);
}
.dense-card h3 {
  margin: 0 0 8px;
  font-size: 1.05rem;
  font-weight: 800;
}
.dense-card p { margin: 0 0 8px; font-size: 0.98rem; }
.dense-card p:last-child { margin-bottom: 0; }
.dense-card svg { width: 28px; height: 28px; margin-bottom: 10px; }

.steps {
  list-style: none;
  margin: 18px 0 0;
  padding: 0;
  counter-reset: step;
  display: grid;
  gap: 10px;
}
.steps li {
  border: 2px solid var(--ink);
  padding: 14px 16px 14px 58px;
  position: relative;
}
.steps li::before {
  counter-increment: step;
  content: counter(step);
  position: absolute;
  left: 12px;
  top: 14px;
  width: 32px;
  height: 32px;
  border: 2px solid var(--ink);
  display: grid;
  place-items: center;
  font-weight: 800;
}

.table-wrap { overflow: auto; margin-top: 16px; }
table {
  width: 100%;
  border-collapse: collapse;
  min-width: 640px;
}
th, td {
  border: 2px solid var(--ink);
  padding: 10px 12px;
  text-align: left;
  vertical-align: top;
}
th { background: var(--ink); color: var(--paper); font-weight: 700; }
tr:nth-child(even) td { background: var(--wash); }

.split {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-top: 16px;
}
.split article {
  border: 2px solid var(--ink);
  padding: 16px 18px;
}
.split h3 { margin: 0 0 8px; font-size: 1.05rem; }

.faq { margin-top: 10px; }
.faq-item {
  border-bottom: 2px solid var(--ink);
  padding: 16px 0;
}
.faq-item h3 {
  margin: 0 0 8px;
  font-size: 1.05rem;
  font-weight: 800;
}
.faq-item p { margin: 0; }

.site-footer {
  background: var(--ink);
  color: var(--paper);
  padding: 28px 0 36px;
  font-size: 0.92rem;
}
.site-footer p { margin: 0 0 10px; }
.site-footer p:last-child { margin-bottom: 0; }

@media (max-width: 860px) {
  .dense-grid, .split { grid-template-columns: 1fr; }
  .hero h1 { max-width: none; }
  .site-header .wrap { flex-direction: column; align-items: flex-start; padding: 12px 0; }
}