/* digital-watermarking · 全站布局、导航、卡片与响应式 */
body { min-width: 0; }

.topbar {
  position: sticky;
  top: 0;
  z-index: 30;
  display: flex;
  align-items: center;
  gap: 14px;
  min-height: 64px;
  padding: 12px max(20px, calc((100vw - 1240px) / 2));
  border-bottom: 1px solid color-mix(in srgb, var(--border) 82%, transparent);
  background: color-mix(in srgb, var(--bg) 86%, transparent);
  backdrop-filter: saturate(170%) blur(18px);
}

.topbar .brand {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  color: var(--text);
  font-size: 14px;
  font-weight: 720;
  letter-spacing: -.02em;
  white-space: nowrap;
}

.topbar .brand::before {
  content: '';
  width: 18px;
  height: 18px;
  border: 1px solid color-mix(in srgb, var(--accent) 65%, var(--border));
  border-radius: 5px;
  background:
    radial-gradient(circle at 35% 35%, var(--accent-2) 0 2px, transparent 3px),
    linear-gradient(135deg, color-mix(in srgb, var(--accent) 25%, transparent), transparent 55%),
    var(--surface);
  box-shadow: inset 0 0 0 4px color-mix(in srgb, var(--accent) 8%, transparent), 0 0 18px color-mix(in srgb, var(--accent) 18%, transparent);
}

.topbar .brand:hover { color: var(--accent); text-decoration: none; }
.topbar .spacer { flex: 1; }
.topbar nav { display: flex; align-items: center; gap: 7px; }
.topbar nav a {
  padding: 6px 9px;
  border-radius: 999px;
  color: var(--text-soft);
  font-size: 13px;
  white-space: nowrap;
  transition: color .15s, background .15s;
}
.topbar nav a:hover { background: var(--accent-bg); color: var(--accent); text-decoration: none; }
.topbar nav a[aria-current="page"] { background: var(--accent-bg); color: var(--accent); }

.wrap { width: min(100%, 1120px); margin: 0 auto; padding: 0 24px 88px; }
.wrap--wide { width: min(100%, 1240px); }

.page-head {
  position: relative;
  max-width: 930px;
  padding: 72px 0 36px;
}

.page-head::before {
  content: attr(data-section);
  display: block;
  min-height: 1em;
  margin-bottom: 15px;
  color: var(--text-dim);
  font-family: var(--mono);
  font-size: 10px;
  font-weight: 650;
  letter-spacing: .18em;
  text-transform: uppercase;
}

.page-head h1 {
  max-width: 18ch;
  margin: 8px 0 13px;
  font-size: clamp(36px, 6vw, 64px);
  font-weight: 720;
  line-height: 1.06;
  letter-spacing: -.065em;
}

.page-head p { max-width: 70ch; margin: 0; color: var(--text-soft); font-size: 15px; line-height: 1.78; }

.card {
  padding: 22px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: color-mix(in srgb, var(--surface) 96%, var(--accent-bg));
  box-shadow: 0 1px 0 color-mix(in srgb, var(--surface) 80%, transparent);
}
.card + .card { margin-top: 16px; }
.card > :first-child { margin-top: 0; }
.card > :last-child { margin-bottom: 0; }

/* 容量条：载荷占了图片多少可用空间 */
.meter { margin: 12px 0; }
.meter-track {
  height: 6px;
  overflow: hidden;
  border-radius: 999px;
  background: var(--surface-strong);
}
.meter-fill {
  width: 0;
  height: 100%;
  border-radius: 999px;
  background: var(--accent);
  transition: width .18s;
}
.meter--over .meter-fill { background: var(--danger); }
.meter-note { margin: 7px 0 0; color: var(--text-dim); font-size: 13px; }
.meter--over .meter-note { color: var(--danger); }

.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(270px, 1fr)); gap: 14px; }
.cols { display: grid; grid-template-columns: 1fr 1fr; gap: 18px; }
.cols > .field + .field { margin-top: 0; }

.tile {
  position: relative;
  display: block;
  min-height: 150px;
  padding: 20px;
  overflow: hidden;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--text);
  transition: transform .18s, border-color .18s, box-shadow .18s;
}
.tile::after {
  content: '↗';
  position: absolute;
  right: 18px;
  bottom: 15px;
  color: var(--text-dim);
  font-family: var(--mono);
  transition: color .18s, transform .18s;
}
.tile:hover { border-color: var(--border-hi); box-shadow: var(--shadow-hi); text-decoration: none; transform: translateY(-3px); }
.tile:hover::after { color: var(--accent); transform: translate(2px, -2px); }
.tile h3 { display: flex; align-items: center; gap: 8px; margin: 0 0 7px; padding-right: 30px; font-size: 16px; }
.tile p { margin: 0; color: var(--text-soft); font-size: 13.5px; line-height: 1.65; }
.tile--feature { border-color: color-mix(in srgb, var(--accent) 46%, var(--border)); background: linear-gradient(145deg, var(--accent-bg), var(--surface) 72%); }

.section-heading {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 20px;
  align-items: end;
  margin: 72px 0 22px;
}
.section-heading h2 { max-width: 22ch; margin: 0; font-size: clamp(30px, 4.7vw, 54px); line-height: 1.08; }
.section-heading p { max-width: 43ch; margin: 0; color: var(--text-soft); }
.section-label { color: var(--text-dim); font-family: var(--mono); font-size: 10px; font-weight: 650; letter-spacing: .17em; text-transform: uppercase; }

.tool-page .page-head { max-width: 900px; }
.tool-page .page-head h1 { font-size: clamp(36px, 5vw, 56px); }
.tool-page .page-head + .note { margin-bottom: 18px; }
.tool-page .card { box-shadow: var(--shadow); }

.principle-brief {
  margin-top: 54px;
  padding: 28px;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--surface);
}
.principle-brief h2 { margin: 0 0 8px; }
.principle-brief > p { max-width: 72ch; margin: 0; color: var(--text-soft); }

.boundary-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; margin-top: 22px; }
.boundary-item { padding: 16px; border: 1px solid var(--border); border-radius: 12px; background: color-mix(in srgb, var(--surface) 88%, transparent); }
.boundary-item strong { display: block; margin-bottom: 5px; color: var(--text); font-size: 12px; }
.boundary-item p { margin: 0; color: var(--text-soft); font-size: 12px; }
.boundary-item--limit { border-color: color-mix(in srgb, var(--warn) 28%, var(--border)); }

.related-tools { margin-top: 34px; padding-top: 22px; border-top: 1px solid var(--border); }
.related-tools strong { display: block; margin-bottom: 10px; font-size: 13px; }
.related-tools .btn { min-height: 36px; padding: 7px 12px; }

footer.site {
  margin-top: 72px;
  padding: 28px 0 12px;
  border-top: 1px solid var(--border);
  color: var(--text-dim);
  font-size: 12.5px;
}
.site-nav { display: grid; grid-template-columns: repeat(auto-fit, minmax(160px, 1fr)); gap: 7px 18px; margin-bottom: 20px; }
.site-nav a { color: var(--text-soft); font-size: 12.5px; }
.site-nav a:hover { color: var(--accent); }

@media (max-width: 760px) {
  .topbar { gap: 10px; min-height: 56px; padding: 9px 16px; }
  .topbar .spacer { display: none; }
  .topbar nav { flex: 1; gap: 3px; overflow-x: auto; scrollbar-width: none; }
  .topbar nav::-webkit-scrollbar { display: none; }
  .topbar nav a { padding: 5px 7px; }
  .wrap { padding: 0 16px 68px; }
  .page-head { padding: 52px 0 28px; }
  .page-head h1 { letter-spacing: -.05em; }
  .cols { grid-template-columns: 1fr; }
  .section-heading { grid-template-columns: 1fr; margin-top: 56px; }
  .section-heading h2 { max-width: 18ch; }
  .card { padding: 18px; }
  .tile { min-height: 138px; }
  .principle-brief { padding: 22px 18px; }
  .boundary-grid { grid-template-columns: 1fr; }
  .site-nav { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 430px) {
  .topbar .brand { font-size: 0; }
  .topbar .brand::before { width: 20px; height: 20px; }
  .site-nav { grid-template-columns: 1fr; }
}