/* ============================================================
   必一体育主站 · 共享样式 /assets/site.css
   战术室蓝图体系：炭黑 + 深墨绿 + 青柠绿信号 + 橙红刻度
   ============================================================ */

/* ---------- 1. 设计令牌 ---------- */
:root {
  --by-ink: #0B0F0D;
  --by-forest: #111A16;
  --by-panel: #16231D;
  --by-panel-2: #1B2A23;
  --by-glass: rgba(23, 38, 31, 0.72);
  --by-line: #2A3B33;
  --by-line-soft: rgba(42, 59, 51, 0.5);
  --by-text: #E8F1EA;
  --by-muted: #A7B8AE;
  --by-dim: #6F8F7C;
  --by-lime: #C7FF3D;
  --by-ember: #FF6B3D;
  --by-focus: #E6FF8A;

  --by-font-display: "Barlow Condensed", "Oswald", "Noto Sans SC", "Source Han Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --by-font-body: "Noto Sans SC", "Source Han Sans SC", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, -apple-system, sans-serif;
  --by-font-mono: "IBM Plex Mono", "JetBrains Mono", "Roboto Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;

  --by-shell: 1320px;
  --by-gutter: clamp(16px, 3.2vw, 40px);
  --by-radius: 3px;
  --by-header-h: 72px;
  --by-ease: cubic-bezier(0.22, 0.61, 0.36, 1);
  --by-shadow: 0 18px 40px -24px rgba(0, 0, 0, 0.9);
}

/* ---------- 2. Reset ---------- */
*,
*::before,
*::after { box-sizing: border-box; }

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--by-header-h) + 20px);
}

body {
  margin: 0;
  padding-top: var(--by-header-h);
  font-family: var(--by-font-body);
  font-size: 16px;
  font-weight: 400;
  line-height: 1.75;
  color: var(--by-text);
  background-color: var(--by-ink);
  background-image:
    radial-gradient(1200px 620px at 84% -12%, rgba(199, 255, 61, 0.075), transparent 66%),
    radial-gradient(900px 520px at -6% 24%, rgba(255, 107, 61, 0.055), transparent 70%),
    linear-gradient(var(--by-line-soft) 1px, transparent 1px),
    linear-gradient(90deg, var(--by-line-soft) 1px, transparent 1px);
  background-size: auto, auto, 96px 96px, 96px 96px;
  background-position: center top, center top, center top, center top;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

body.by-nav-open { overflow: hidden; }

h1, h2, h3, h4, h5, h6 {
  margin: 0;
  font-family: var(--by-font-display);
  font-weight: 800;
  line-height: 1.06;
  letter-spacing: 0.005em;
  color: var(--by-text);
}

p { margin: 0; }
img, svg, video { display: block; max-width: 100%; height: auto; }
ul, ol { margin: 0; padding: 0; list-style: none; }
a { color: inherit; text-decoration: none; }
button { font: inherit; color: inherit; background: none; border: 0; padding: 0; cursor: pointer; }
table { border-collapse: collapse; width: 100%; }
hr { border: 0; height: 1px; background: var(--by-line); margin: 0; }

::selection { background: rgba(199, 255, 61, 0.3); color: #FFFFFF; }

/* ---------- 3. 焦点与可访问性 ---------- */
a:focus-visible,
button:focus-visible,
summary:focus-visible,
[tabindex]:focus-visible,
input:focus-visible {
  outline: 2px solid var(--by-focus);
  outline-offset: 3px;
  border-radius: 2px;
}

.by-skip {
  position: fixed;
  top: 10px;
  left: 10px;
  z-index: 300;
  padding: 10px 18px;
  font-size: 14px;
  font-weight: 700;
  letter-spacing: 0.04em;
  color: #0B0F0D;
  background: var(--by-lime);
  border-radius: 2px;
  transform: translateY(-180%);
  transition: transform 0.18s var(--by-ease);
}
.by-skip:focus,
.by-skip:focus-visible { transform: translateY(0); }

/* ---------- 4. 排版与容器 ---------- */
.by-shell {
  width: 100%;
  max-width: var(--by-shell);
  margin-inline: auto;
  padding-inline: var(--by-gutter);
}

.by-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 5px 10px;
  font-family: var(--by-font-mono);
  font-size: 12px;
  line-height: 1.4;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--by-muted);
  background: rgba(22, 35, 29, 0.6);
  border: 1px solid var(--by-line);
  border-radius: 2px;
}

.by-lede {
  max-width: 66ch;
  font-size: clamp(16px, 1.6vw, 18px);
  line-height: 1.8;
  color: var(--by-muted);
}

.by-prose {
  max-width: 68ch;
  font-size: 16px;
  line-height: 1.85;
  color: var(--by-muted);
}
.by-prose > * + * { margin-top: 1em; }
.by-prose strong { color: var(--by-text); font-weight: 700; }
.by-prose h2,
.by-prose h3 {
  color: var(--by-text);
  margin-top: 1.5em;
  font-size: clamp(22px, 2.6vw, 30px);
}
.by-prose a {
  color: var(--by-lime);
  border-bottom: 1px solid rgba(199, 255, 61, 0.35);
}
.by-prose ul { list-style: none; padding: 0; }
.by-prose li {
  position: relative;
  padding-left: 18px;
  margin-top: 0.45em;
}
.by-prose li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.78em;
  width: 9px;
  height: 1px;
  background: var(--by-lime);
}

.by-link {
  color: var(--by-lime);
  border-bottom: 1px solid rgba(199, 255, 61, 0.4);
  transition: color 0.16s var(--by-ease), background 0.16s var(--by-ease);
}
.by-link:hover { color: var(--by-focus); background: rgba(199, 255, 61, 0.12); }

.by-divider {
  height: 1px;
  margin-block: clamp(24px, 4vw, 48px);
  background: var(--by-line);
}

/* ---------- 5. 栅格与章节 ---------- */
.by-grid {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: clamp(16px, 2.2vw, 28px);
}
.by-col-3 { grid-column: span 3; }
.by-col-4 { grid-column: span 4; }
.by-col-5 { grid-column: span 5; }
.by-col-6 { grid-column: span 6; }
.by-col-7 { grid-column: span 7; }
.by-col-8 { grid-column: span 8; }
.by-col-9 { grid-column: span 9; }
.by-col-12 { grid-column: span 12; }

.by-section { padding-block: clamp(32px, 5vw, 64px); }

.by-section__head {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-end;
  gap: 12px 24px;
  margin-bottom: clamp(20px, 3vw, 32px);
  padding-bottom: 14px;
  border-bottom: 1px solid var(--by-line);
}

.by-section__index {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: var(--by-font-mono);
  font-size: 12px;
  letter-spacing: 0.18em;
  color: var(--by-lime);
}
.by-section__index::before {
  content: "";
  width: 22px;
  height: 1px;
  background: var(--by-lime);
}

.by-section__title {
  font-size: clamp(26px, 3.6vw, 42px);
  letter-spacing: -0.01em;
}

.by-section__note {
  margin-left: auto;
  font-family: var(--by-font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--by-muted);
}

/* ---------- 6. 按钮 ---------- */
.by-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 18px;
  font-family: var(--by-font-body);
  font-size: 14px;
  font-weight: 600;
  line-height: 1.4;
  letter-spacing: 0.04em;
  color: var(--by-text);
  background: transparent;
  border: 1px solid var(--by-line);
  border-radius: 2px;
  transition: color 0.16s var(--by-ease), background 0.16s var(--by-ease), border-color 0.16s var(--by-ease), box-shadow 0.16s var(--by-ease);
}
.by-btn:hover {
  color: var(--by-lime);
  border-color: var(--by-lime);
  background: rgba(199, 255, 61, 0.08);
}

.by-btn--primary {
  color: #0B0F0D;
  background: var(--by-lime);
  border-color: var(--by-lime);
  font-weight: 700;
}
.by-btn--primary:hover {
  color: #0B0F0D;
  background: var(--by-focus);
  border-color: var(--by-focus);
  box-shadow: 0 0 0 4px rgba(199, 255, 61, 0.14);
}

.by-btn--ghost {
  color: var(--by-muted);
  background: rgba(22, 35, 29, 0.6);
}
.by-btn--ghost:hover { color: var(--by-lime); }

.by-btn--quiet {
  padding: 7px 12px;
  font-size: 13px;
  color: var(--by-dim);
  border-color: transparent;
}
.by-btn--quiet:hover {
  color: var(--by-lime);
  background: rgba(199, 255, 61, 0.08);
  border-color: transparent;
}

/* ---------- 7. 面包屑 ---------- */
.by-breadcrumb {
  padding-block: 16px 0;
  font-family: var(--by-font-mono);
  font-size: 12px;
  letter-spacing: 0.1em;
  color: var(--by-dim);
}
.by-breadcrumb__list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
}
.by-breadcrumb__item {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  min-width: 0;
}
.by-breadcrumb__item + .by-breadcrumb__item::before {
  content: "/";
  color: var(--by-line);
}
.by-breadcrumb__link {
  color: var(--by-muted);
  transition: color 0.16s var(--by-ease);
}
.by-breadcrumb__link:hover { color: var(--by-lime); }
.by-breadcrumb__current { color: var(--by-text); }

/* ---------- 8. 承载面与标签 ---------- */
.by-card {
  position: relative;
  padding: clamp(16px, 2vw, 24px);
  background: var(--by-panel);
  border: 1px solid var(--by-line);
  border-radius: var(--by-radius);
  transition: border-color 0.16s var(--by-ease), background 0.16s var(--by-ease);
}
.by-card:hover {
  border-color: rgba(199, 255, 61, 0.42);
  background: var(--by-panel-2);
}
.by-card--diag {
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 16px), 0 100%);
}
.by-card__head {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 8px 12px;
  margin-bottom: 12px;
  padding-bottom: 10px;
  border-bottom: 1px dashed var(--by-line);
}
.by-card__title {
  font-size: clamp(18px, 2vw, 24px);
  letter-spacing: 0.01em;
}
.by-card__meta {
  margin-left: auto;
  font-family: var(--by-font-mono);
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--by-muted);
}
.by-card__body {
  font-size: 15px;
  line-height: 1.75;
  color: var(--by-muted);
}

.by-glass {
  background: var(--by-glass);
  border: 1px solid rgba(42, 59, 51, 0.9);
  border-radius: var(--by-radius);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

.by-taglist {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}
.by-tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  font-size: 13px;
  line-height: 1.4;
  letter-spacing: 0.02em;
  color: var(--by-muted);
  background: rgba(22, 35, 29, 0.7);
  border: 1px solid var(--by-line);
  border-radius: 999px;
  transition: color 0.16s var(--by-ease), border-color 0.16s var(--by-ease), background 0.16s var(--by-ease);
}
.by-tag:hover {
  color: var(--by-text);
  border-color: var(--by-dim);
}
.by-tag[aria-pressed="true"],
.by-tag--active {
  color: var(--by-lime);
  background: rgba(199, 255, 61, 0.14);
  border-color: var(--by-lime);
}

.by-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 3px 8px;
  font-family: var(--by-font-mono);
  font-size: 11px;
  line-height: 1.5;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--by-muted);
  border: 1px solid var(--by-line);
  border-radius: 2px;
}
.by-badge--lime {
  color: var(--by-lime);
  border-color: rgba(199, 255, 61, 0.5);
  background: rgba(199, 255, 61, 0.1);
}
.by-badge--ember {
  color: var(--by-ember);
  border-color: rgba(255, 107, 61, 0.5);
  background: rgba(255, 107, 61, 0.1);
}

.by-note {
  padding: 8px 0 8px 12px;
  font-size: 13px;
  line-height: 1.7;
  color: var(--by-dim);
  background: rgba(255, 107, 61, 0.06);
  border-left: 2px solid var(--by-ember);
}
.by-empty {
  padding: 24px;
  font-size: 14px;
  text-align: center;
  color: var(--by-dim);
  border: 1px dashed var(--by-line);
  border-radius: var(--by-radius);
}

/* ---------- 9. 数据组件 ---------- */
.by-stat {
  display: flex;
  flex-direction: column;
  gap: 4px;
  min-width: 0;
}
.by-stat__value {
  font-family: var(--by-font-mono);
  font-size: clamp(28px, 4vw, 44px);
  line-height: 1;
  letter-spacing: -0.02em;
  color: var(--by-text);
  font-variant-numeric: tabular-nums;
}
.by-stat__label {
  font-family: var(--by-font-mono);
  font-size: 11px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--by-dim);
}

.by-table__wrap {
  max-height: min(70vh, 560px);
  overflow: auto;
  background: var(--by-panel);
  border: 1px solid var(--by-line);
  border-radius: var(--by-radius);
}
.by-table {
  width: 100%;
  min-width: 540px;
  font-size: 14px;
}
.by-table__caption {
  caption-side: top;
  padding: 10px 14px;
  font-family: var(--by-font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  text-align: left;
  color: var(--by-dim);
  background: var(--by-forest);
  border-bottom: 1px solid var(--by-line);
}
.by-table th,
.by-table td {
  padding: 10px 14px;
  text-align: left;
  white-space: nowrap;
  border-bottom: 1px solid var(--by-line-soft);
}
.by-table thead th {
  position: sticky;
  top: 0;
  z-index: 1;
  font-family: var(--by-font-mono);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--by-muted);
  background: var(--by-forest);
  border-bottom: 1px solid var(--by-line);
}
.by-table tbody tr { transition: background 0.16s var(--by-ease); }
.by-table tbody tr:hover { background: rgba(199, 255, 61, 0.055); }
.by-table tbody tr:last-child td { border-bottom: 0; }
.by-num {
  font-family: var(--by-font-mono);
  font-variant-numeric: tabular-nums;
  letter-spacing: 0.02em;
}

.by-meter {
  display: flex;
  align-items: flex-end;
  gap: 3px;
  height: 64px;
}
.by-meter__bar {
  flex: 1 1 0;
  min-height: 2px;
  background: linear-gradient(180deg, var(--by-lime), rgba(199, 255, 61, 0.22));
  border-radius: 1px 1px 0 0;
  transition: height 0.24s var(--by-ease);
}
.by-meter__bar--ember {
  background: linear-gradient(180deg, var(--by-ember), rgba(255, 107, 61, 0.22));
}
.by-meter__axis {
  display: flex;
  justify-content: space-between;
  margin-top: 6px;
  font-family: var(--by-font-mono);
  font-size: 10px;
  letter-spacing: 0.06em;
  color: var(--by-dim);
}

/* ---------- 10. 阅读辅助 ---------- */
.by-toc {
  position: sticky;
  top: calc(var(--by-header-h) + 18px);
  font-size: 13px;
}
.by-toc__title {
  margin-bottom: 10px;
  padding-bottom: 8px;
  font-family: var(--by-font-mono);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--by-dim);
  border-bottom: 1px solid var(--by-line);
}
.by-toc__list {
  display: flex;
  flex-direction: column;
}
.by-toc__link {
  display: block;
  padding: 7px 8px 7px 14px;
  color: var(--by-muted);
  border-left: 1px solid var(--by-line);
  transition: color 0.16s var(--by-ease), border-color 0.16s var(--by-ease), background 0.16s var(--by-ease);
}
.by-toc__link:hover {
  color: var(--by-text);
  border-color: var(--by-dim);
}
.by-toc__link[aria-current="true"] {
  color: var(--by-lime);
  border-color: var(--by-lime);
  background: linear-gradient(90deg, rgba(199, 255, 61, 0.12), transparent 80%);
}

.by-timeline {
  position: relative;
  margin-left: 6px;
  padding: 0;
  list-style: none;
  border-left: 1px solid var(--by-line);
}
.by-timeline__item {
  position: relative;
  padding: 0 0 26px 22px;
}
.by-timeline__item::before {
  content: "";
  position: absolute;
  left: -4px;
  top: 6px;
  width: 7px;
  height: 7px;
  background: var(--by-ink);
  border: 1px solid var(--by-dim);
  border-radius: 50%;
  transition: background 0.16s var(--by-ease), box-shadow 0.16s var(--by-ease), border-color 0.16s var(--by-ease);
}
.by-timeline__item[aria-current="true"]::before {
  background: var(--by-lime);
  border-color: var(--by-lime);
  box-shadow: 0 0 0 4px rgba(199, 255, 61, 0.16);
}
.by-timeline__label {
  display: block;
  margin-bottom: 2px;
  font-family: var(--by-font-mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--by-ember);
}
.by-timeline__text {
  font-size: 14px;
  line-height: 1.65;
  color: var(--by-muted);
}

/* ---------- 11. 图片容器 ---------- */
.by-media {
  position: relative;
  display: block;
  overflow: hidden;
  width: 100%;
  background:
    linear-gradient(155deg, #16231D 0%, #0B0F0D 62%),
    var(--by-panel);
  border: 1px solid var(--by-line);
  border-radius: var(--by-radius);
}
.by-media::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(135deg, rgba(199, 255, 61, 0.16), transparent 58%),
    repeating-linear-gradient(90deg, rgba(42, 59, 51, 0.6) 0 1px, transparent 1px 28px),
    repeating-linear-gradient(0deg, rgba(42, 59, 51, 0.4) 0 1px, transparent 1px 28px);
  pointer-events: none;
}
.by-media img {
  position: relative;
  width: 100%;
  height: 100%;
  object-fit: cover;
}
.by-media--wide { aspect-ratio: 16 / 9; }
.by-media--tall { aspect-ratio: 3 / 4; }
.by-media--square { aspect-ratio: 1 / 1; }
.by-media--diag { clip-path: polygon(0 0, 100% 0, 100% 92%, 0 100%); }
.by-media__tag {
  position: absolute;
  left: 12px;
  bottom: 12px;
  z-index: 2;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 10px;
  font-family: var(--by-font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  color: var(--by-lime);
  background: rgba(11, 15, 13, 0.78);
  border: 1px solid rgba(199, 255, 61, 0.45);
  border-radius: 2px;
}

/* ---------- 12. 显现动效 ---------- */
.by-js [data-reveal] {
  opacity: 0;
  transform: translateY(14px);
}
.by-js [data-reveal].is-in {
  opacity: 1;
  transform: none;
  transition: opacity 0.42s var(--by-ease), transform 0.42s var(--by-ease);
}

/* ---------- 13. 页头 ---------- */
.by-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 120;
  background: linear-gradient(180deg, rgba(11, 15, 13, 0.985) 0%, rgba(17, 26, 22, 0.965) 100%);
  border-bottom: 1px solid var(--by-line);
  box-shadow: 0 12px 32px -24px rgba(0, 0, 0, 0.95);
}

.by-header__rail {
  position: relative;
  height: 4px;
  background-color: rgba(42, 59, 51, 0.55);
  background-image: repeating-linear-gradient(90deg, var(--by-line) 0 1px, transparent 1px 26px);
}
.by-header__rail::before {
  content: "";
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  width: clamp(64px, 18vw, 180px);
  background: var(--by-lime);
  opacity: 0.9;
}

.by-header__inner {
  display: grid;
  grid-template-columns: auto 1fr auto;
  align-items: center;
  gap: clamp(12px, 2vw, 28px);
  width: 100%;
  max-width: var(--by-shell);
  min-height: calc(var(--by-header-h) - 6px);
  margin-inline: auto;
  padding-inline: var(--by-gutter);
}

.by-brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  min-width: 0;
  min-height: 44px;
}
.by-brand__mark {
  display: grid;
  place-items: center;
  flex: none;
  width: 38px;
  height: 38px;
  font-family: var(--by-font-mono);
  font-size: 14px;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--by-lime);
  background: rgba(199, 255, 61, 0.1);
  border: 1px solid rgba(199, 255, 61, 0.55);
  border-radius: 2px;
  clip-path: polygon(0 0, 100% 0, 100% 72%, 78% 100%, 0 100%);
}
.by-brand__text {
  display: flex;
  flex-direction: column;
  min-width: 0;
  line-height: 1.2;
}
.by-brand__name {
  font-family: var(--by-font-display);
  font-size: 15px;
  font-weight: 800;
  letter-spacing: 0.12em;
  white-space: nowrap;
  color: var(--by-text);
  transition: color 0.16s var(--by-ease);
}
.by-brand__badge {
  margin-top: 3px;
  font-family: var(--by-font-mono);
  font-size: 10px;
  letter-spacing: 0.1em;
  white-space: nowrap;
  color: var(--by-dim);
}
.by-brand:hover .by-brand__name { color: var(--by-lime); }

.by-nav {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 2px;
  min-width: 0;
}
.by-nav__list {
  display: flex;
  align-items: center;
  gap: 2px;
  margin: 0;
  padding: 0;
  list-style: none;
}
.by-nav__item { position: relative; }
.by-nav__link {
  position: relative;
  display: inline-block;
  padding: 9px 12px;
  font-size: 14px;
  font-weight: 500;
  letter-spacing: 0.04em;
  color: var(--by-muted);
  border-radius: 2px;
  transition: color 0.16s var(--by-ease), background 0.16s var(--by-ease);
}
.by-nav__link::after {
  content: "";
  position: absolute;
  left: 12px;
  right: 12px;
  bottom: 2px;
  height: 2px;
  background: var(--by-lime);
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform 0.18s var(--by-ease);
}
.by-nav__link:hover {
  color: var(--by-text);
  background: rgba(199, 255, 61, 0.06);
}
.by-nav__link:hover::after { transform: scaleX(1); }
.by-nav__link[aria-current="page"] {
  color: var(--by-lime);
  background: rgba(199, 255, 61, 0.08);
}
.by-nav__link[aria-current="page"]::after { transform: scaleX(1); }

.by-nav__note { display: none; }
.by-nav__cta { display: none; }

.by-header__actions {
  display: flex;
  align-items: center;
  gap: 10px;
  justify-self: end;
}

.by-navtoggle {
  position: relative;
  display: none;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  color: var(--by-text);
  background: rgba(22, 35, 29, 0.75);
  border: 1px solid var(--by-line);
  border-radius: 2px;
  transition: color 0.16s var(--by-ease), border-color 0.16s var(--by-ease);
}
.by-navtoggle:hover {
  color: var(--by-lime);
  border-color: var(--by-lime);
}
.by-navtoggle__bar {
  position: relative;
  display: block;
  width: 18px;
  height: 2px;
  background: currentColor;
  transition: background 0.16s var(--by-ease);
}
.by-navtoggle__bar::before,
.by-navtoggle__bar::after {
  content: "";
  position: absolute;
  left: 0;
  width: 18px;
  height: 2px;
  background: currentColor;
  transition: transform 0.22s var(--by-ease);
}
.by-navtoggle__bar::before { transform: translateY(-6px); }
.by-navtoggle__bar::after { transform: translateY(6px); }
.by-navtoggle[aria-expanded="true"] .by-navtoggle__bar { background: transparent; }
.by-navtoggle[aria-expanded="true"] .by-navtoggle__bar::before {
  background: var(--by-lime);
  transform: rotate(45deg);
}
.by-navtoggle[aria-expanded="true"] .by-navtoggle__bar::after {
  background: var(--by-lime);
  transform: rotate(-45deg);
}
.by-navtoggle__label {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

.by-progress {
  position: relative;
  height: 2px;
  background: rgba(42, 59, 51, 0.6);
}
.by-progress__bar {
  display: block;
  width: 0;
  height: 100%;
  background: linear-gradient(90deg, var(--by-lime) 0%, var(--by-focus) 58%, var(--by-ember) 100%);
  transition: width 0.1s linear;
}

.by-scrim {
  position: fixed;
  inset: 0;
  z-index: 1;
  background: rgba(11, 15, 13, 0.74);
  backdrop-filter: blur(2px);
  -webkit-backdrop-filter: blur(2px);
}
.by-scrim[hidden] { display: none; }

/* ---------- 14. 页脚 ---------- */
.by-footer {
  position: relative;
  margin-top: clamp(48px, 7vw, 96px);
  overflow: hidden;
  background: linear-gradient(180deg, var(--by-forest) 0%, var(--by-ink) 46%);
  border-top: 1px solid var(--by-line);
}
.by-footer::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(var(--by-line-soft) 1px, transparent 1px),
    linear-gradient(90deg, var(--by-line-soft) 1px, transparent 1px);
  background-size: 88px 88px;
  opacity: 0.32;
  pointer-events: none;
}

.by-footer__grid {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: 1.7fr 1fr 1.15fr 0.9fr;
  gap: clamp(24px, 3vw, 44px);
  width: 100%;
  max-width: var(--by-shell);
  margin-inline: auto;
  padding: clamp(36px, 5vw, 68px) var(--by-gutter) clamp(24px, 3vw, 40px);
}

.by-footer__brand { min-width: 0; }
.by-brand--footer .by-brand__name { font-size: 16px; }

.by-footer__intro {
  max-width: 38ch;
  margin-top: 14px;
  font-size: 14px;
  line-height: 1.75;
  color: var(--by-muted);
}
.by-footer__meta {
  display: flex;
  flex-direction: column;
  gap: 6px;
  margin-top: 16px;
}
.by-footer__meta li {
  font-family: var(--by-font-mono);
  font-size: 12px;
  letter-spacing: 0.05em;
  color: var(--by-dim);
}

.by-footer__col { min-width: 0; }
.by-footer__title {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 14px;
  padding-bottom: 10px;
  font-family: var(--by-font-mono);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--by-text);
  border-bottom: 1px solid var(--by-line);
}
.by-footer__title::before {
  content: "";
  flex: none;
  width: 6px;
  height: 6px;
  background: var(--by-lime);
}
.by-footer__list {
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.by-footer__list li {
  font-size: 14px;
  line-height: 1.6;
  color: var(--by-muted);
}
.by-footer__link {
  color: var(--by-muted);
  border-bottom: 1px solid transparent;
  transition: color 0.16s var(--by-ease), border-color 0.16s var(--by-ease);
}
.by-footer__link:hover {
  color: var(--by-lime);
  border-bottom-color: rgba(199, 255, 61, 0.5);
}
.by-footer__hint {
  margin-top: 14px;
  padding-left: 10px;
  font-size: 12px;
  line-height: 1.7;
  color: var(--by-dim);
  border-left: 2px solid var(--by-line);
}

.by-footer__base {
  position: relative;
  z-index: 1;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 8px 24px;
  max-width: var(--by-shell);
  margin-inline: auto;
  padding: 16px var(--by-gutter) 22px;
  font-family: var(--by-font-mono);
  font-size: 11px;
  letter-spacing: 0.08em;
  color: var(--by-dim);
  border-top: 1px solid var(--by-line);
}
.by-footer__copy { margin: 0; }
.by-footer__icp {
  margin: 0;
  color: var(--by-muted);
}

.by-footer__wordmark {
  position: absolute;
  right: -2%;
  bottom: -0.16em;
  z-index: 0;
  font-family: var(--by-font-display);
  font-size: clamp(72px, 16vw, 220px);
  font-weight: 800;
  line-height: 0.8;
  letter-spacing: -0.02em;
  white-space: nowrap;
  color: rgba(199, 255, 61, 0.045);
  pointer-events: none;
  user-select: none;
}

.by-totop {
  position: fixed;
  right: clamp(12px, 2.4vw, 28px);
  bottom: clamp(12px, 2.4vw, 28px);
  z-index: 130;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 46px;
  height: 46px;
  font-family: var(--by-font-mono);
  font-size: 16px;
  line-height: 1;
  color: var(--by-lime);
  background: rgba(22, 35, 29, 0.9);
  border: 1px solid rgba(199, 255, 61, 0.5);
  border-radius: 2px;
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity 0.2s var(--by-ease), transform 0.2s var(--by-ease), visibility 0.2s var(--by-ease), background 0.16s var(--by-ease), color 0.16s var(--by-ease);
}
.by-totop[data-visible] {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}
.by-totop:hover {
  color: var(--by-focus);
  background: rgba(199, 255, 61, 0.16);
  border-color: var(--by-lime);
}
.by-totop__icon { font-size: 16px; }

/* ---------- 15. 响应式 ---------- */
@media (max-width: 1024px) {
  .by-col-3,
  .by-col-4,
  .by-col-5,
  .by-col-6 { grid-column: span 6; }
  .by-col-7,
  .by-col-8,
  .by-col-9 { grid-column: 1 / -1; }

  .by-footer__grid { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 960px) {
  :root { --by-header-h: 64px; }

  .by-header__inner { grid-template-columns: 1fr auto; }

  .by-brand__badge { display: none; }

  .by-nav {
    position: fixed;
    top: var(--by-header-h);
    right: 0;
    bottom: 0;
    z-index: 2;
    display: flex;
    flex-direction: column;
    align-items: stretch;
    justify-content: flex-start;
    gap: 0;
    width: min(88vw, 360px);
    padding: 22px var(--by-gutter) 32px;
    overflow-y: auto;
    background: rgba(17, 26, 22, 0.96);
    border-left: 1px solid var(--by-line);
    box-shadow: -24px 0 44px -30px rgba(0, 0, 0, 0.95);
    transform: translateX(102%);
    opacity: 0;
    visibility: hidden;
    transition: transform 0.26s var(--by-ease), opacity 0.2s var(--by-ease), visibility 0.26s var(--by-ease);
  }
  .by-nav[data-open] {
    transform: translateX(0);
    opacity: 1;
    visibility: visible;
  }

  .by-nav__list {
    flex-direction: column;
    align-items: stretch;
    gap: 2px;
    margin-top: 4px;
  }
  .by-nav__link {
    display: block;
    padding: 13px 12px;
    font-size: 16px;
    border-radius: 2px;
  }
  .by-nav__link::after {
    left: 0;
    right: auto;
    top: 14px;
    bottom: 14px;
    width: 2px;
    height: auto;
    transform: scaleY(0);
    transform-origin: center top;
  }
  .by-nav__link:hover::after,
  .by-nav__link[aria-current="page"]::after { transform: scaleY(1); }

  .by-nav__note {
    display: block;
    margin-top: 18px;
    padding-top: 14px;
    font-family: var(--by-font-mono);
    font-size: 11px;
    line-height: 1.7;
    letter-spacing: 0.06em;
    color: var(--by-dim);
    border-top: 1px solid var(--by-line);
  }
  .by-nav__cta {
    display: inline-flex;
    justify-content: center;
    margin-top: 16px;
  }

  .by-header__cta { display: none; }
  .by-navtoggle { display: inline-flex; }
}

@media (max-width: 680px) {
  .by-col-3,
  .by-col-4,
  .by-col-5,
  .by-col-6 { grid-column: 1 / -1; }

  .by-section__note { margin-left: 0; }

  .by-footer__grid { grid-template-columns: 1fr; }
  .by-footer__base { font-size: 10px; }
  .by-footer__wordmark { font-size: clamp(60px, 22vw, 140px); }
  .by-toc { position: static; }
}

@media (max-width: 400px) {
  .by-brand__name { font-size: 13px; letter-spacing: 0.08em; }
  .by-brand__mark { width: 34px; height: 34px; font-size: 13px; }
}

/* ---------- 16. 减弱动效 ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }

  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }

  .by-js [data-reveal] {
    opacity: 1;
    transform: none;
  }
  .by-totop { transform: none; }
  .by-nav { transition: none; }
}