/* ==========================================================================
   博鱼官网 · 共享样式 /assets/site.css
   深海蓝基底 + 电光青信号 + 珊瑚橙行动点
   ========================================================================== */

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body, h1, h2, h3, h4, h5, p, ul, ol, dl, dt, dd, figure, blockquote {
  margin: 0;
}

ul, ol { padding: 0; list-style: none; }

img, svg, video { max-width: 100%; }

:root {
  --by-deep-sea: #0A2540;
  --by-tide: #0E3A5C;
  --by-electric: #00D4FF;
  --by-electric-soft: #7FE7FF;
  --by-coral: #FF6B4A;
  --by-sand: #F7F4EE;
  --by-pearl: #D9E2EC;
  --by-ink: #07131F;
  --by-lake: #2E8B9E;

  --by-grad-signal: linear-gradient(115deg, #1B6B8C 0%, #00D4FF 100%);
  --by-grad-panel: linear-gradient(158deg, #0E3A5C 0%, #0A2540 62%, #07131F 100%);
  --by-grad-wake: radial-gradient(120% 90% at 10% 0%, rgba(0, 212, 255, .20) 0%, rgba(0, 212, 255, 0) 58%);

  --by-line: rgba(127, 231, 255, .22);
  --by-line-strong: rgba(0, 212, 255, .62);
  --by-shadow-card: 10px 10px 0 rgba(7, 19, 31, .55);
  --by-shadow-card-hover: 14px 16px 0 rgba(7, 19, 31, .62);

  --by-radius-s: 8px;
  --by-radius-m: 14px;
  --by-radius-l: 20px;

  --by-font-head: "Inter Tight", "Montserrat", "HarmonyOS Sans SC", "PingFang SC", "Source Han Sans SC", "Noto Sans SC", system-ui, sans-serif;
  --by-font-body: "Source Han Sans SC", "Noto Sans SC", "PingFang SC", "HarmonyOS Sans SC", "Microsoft YaHei", system-ui, sans-serif;
  --by-font-mono: "JetBrains Mono", "SFMono-Regular", ui-monospace, Consolas, "HarmonyOS Sans SC", monospace;

  --by-header-h: 76px;
  --by-shell: 1280px;
  --by-gutter: clamp(18px, 4vw, 44px);
}

body {
  min-height: 100vh;
  background: var(--by-deep-sea);
  color: var(--by-pearl);
  font-family: var(--by-font-body);
  font-size: 17px;
  line-height: 1.75;
  letter-spacing: .005em;
  text-wrap: pretty;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4 {
  font-family: var(--by-font-head);
  font-weight: 800;
  line-height: 1.16;
  letter-spacing: .02em;
  color: var(--by-sand);
  text-wrap: balance;
}

h1 { font-size: clamp(2.3rem, 5.4vw, 4.6rem); }
h2 { font-size: clamp(1.8rem, 3.4vw, 2.8rem); }
h3 { font-size: clamp(1.18rem, 1.9vw, 1.5rem); }
h4 { font-size: 1.05rem; }

p { font-size: inherit; }

a {
  color: var(--by-electric-soft);
  text-decoration: none;
  transition: color .2s ease, border-color .2s ease, background-color .2s ease;
}

a:hover { color: var(--by-electric); }

:focus-visible {
  outline: 3px solid var(--by-coral);
  outline-offset: 3px;
  border-radius: 4px;
}

section[id], div[id], article[id], main[id] {
  scroll-margin-top: calc(var(--by-header-h) + 20px);
}

/* ---------- 工具类 ---------- */

.by-visually-hidden {
  position: absolute !important;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

.by-mono {
  font-family: var(--by-font-mono);
  font-variant-numeric: tabular-nums;
}

.by-container {
  width: min(100%, var(--by-shell));
  margin: 0 auto;
  padding: 0 var(--by-gutter);
}

.by-divider {
  height: 2px;
  border: 0;
  margin: clamp(28px, 5vw, 54px) 0;
  background: linear-gradient(90deg, rgba(0, 212, 255, .6) 0%, rgba(127, 231, 255, .12) 60%, rgba(255, 107, 74, .5) 100%);
}

/* ---------- 页眉 ---------- */

.by-skip {
  position: absolute;
  left: var(--by-gutter);
  top: 0;
  z-index: 200;
  transform: translateY(-170%);
  padding: 11px 20px;
  border-radius: 0 0 12px 12px;
  background: var(--by-coral);
  color: #2A0D05;
  font-family: var(--by-font-head);
  font-size: 14px;
  font-weight: 800;
  letter-spacing: .06em;
  box-shadow: 0 10px 22px rgba(0, 0, 0, .45);
  transition: transform .22s ease;
}

.by-skip:focus,
.by-skip:focus-visible {
  transform: translateY(0);
  color: #2A0D05;
}

.by-header {
  position: sticky;
  top: 0;
  z-index: 120;
  isolation: isolate;
  background: linear-gradient(180deg, #0A2540 0%, #0A2540 100%);
  border-bottom: 2px solid var(--by-line);
}

.by-header::after {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background: var(--by-grad-wake);
}

.by-header__inner {
  position: relative;
  z-index: 1;
  width: min(100%, var(--by-shell));
  margin: 0 auto;
  padding: 0 var(--by-gutter);
  min-height: var(--by-header-h);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 26px;
}

.by-header__brand-zone {
  display: flex;
  align-items: center;
  gap: 20px;
  min-width: 0;
}

.by-brand {
  display: flex;
  align-items: center;
  gap: 12px;
  color: var(--by-sand);
}

.by-brand:hover { color: var(--by-sand); }

.by-brand__mark {
  position: relative;
  flex: 0 0 auto;
  width: 42px;
  height: 42px;
  border-radius: 15px 15px 15px 5px;
  background: linear-gradient(135deg, var(--by-electric) 0%, var(--by-lake) 58%, var(--by-deep-sea) 100%);
  border: 2px solid rgba(127, 231, 255, .58);
  box-shadow: 0 0 0 4px rgba(0, 212, 255, .09), 0 8px 20px rgba(3, 11, 19, .5);
}

.by-brand__mark::after {
  content: "";
  position: absolute;
  right: 7px;
  bottom: 7px;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--by-coral);
  box-shadow: 0 0 12px var(--by-coral);
}

.by-brand__text {
  display: flex;
  flex-direction: column;
  line-height: 1.2;
  min-width: 0;
}

.by-brand__name {
  font-family: var(--by-font-head);
  font-size: 19px;
  font-weight: 800;
  letter-spacing: .07em;
  color: var(--by-sand);
  white-space: nowrap;
}

.by-brand__meta {
  font-family: var(--by-font-mono);
  font-size: 10.5px;
  letter-spacing: .2em;
  text-transform: uppercase;
  color: rgba(127, 231, 255, .7);
  white-space: nowrap;
}

.by-status {
  display: flex;
  align-items: center;
  gap: 9px;
  padding: 5px 13px 5px 11px;
  border: 1.5px solid var(--by-line);
  border-radius: 999px;
  background: rgba(14, 58, 92, .62);
  font-family: var(--by-font-mono);
  font-size: 11.5px;
  letter-spacing: .1em;
  color: var(--by-electric-soft);
  white-space: nowrap;
}

.by-status__dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--by-electric);
  box-shadow: 0 0 0 4px rgba(0, 212, 255, .16), 0 0 12px var(--by-electric);
  animation: by-breathe 2.8s ease-in-out infinite;
}

.by-status__label {
  font-weight: 700;
  color: var(--by-coral);
}

.by-status__text { color: rgba(217, 226, 236, .74); }

@keyframes by-breathe {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: .58; transform: scale(.86); }
}

.by-navtoggle {
  display: none;
  align-items: center;
  gap: 10px;
  padding: 10px 15px;
  border: 1.5px solid var(--by-line);
  border-radius: var(--by-radius-m);
  background: rgba(14, 58, 92, .78);
  color: var(--by-sand);
  font-family: var(--by-font-head);
  font-size: 14px;
  font-weight: 800;
  letter-spacing: .08em;
  cursor: pointer;
  transition: border-color .2s ease, background-color .2s ease;
}

.by-navtoggle:hover { border-color: var(--by-line-strong); }

.by-navtoggle__bars {
  display: inline-flex;
  flex-direction: column;
  gap: 4px;
  width: 18px;
}

.by-navtoggle__bars span {
  display: block;
  height: 2px;
  width: 100%;
  border-radius: 2px;
  background: var(--by-electric);
  transform-origin: center;
  transition: transform .25s ease, opacity .25s ease, width .25s ease;
}

.by-navtoggle__bars span:nth-child(2) { width: 70%; }
.by-navtoggle__bars span:nth-child(3) { width: 55%; }

.by-navtoggle[aria-expanded="true"] { border-color: var(--by-line-strong); }
.by-navtoggle[aria-expanded="true"] .by-navtoggle__bars span:nth-child(1) { transform: translateY(6px) rotate(45deg); width: 100%; }
.by-navtoggle[aria-expanded="true"] .by-navtoggle__bars span:nth-child(2) { opacity: 0; }
.by-navtoggle[aria-expanded="true"] .by-navtoggle__bars span:nth-child(3) { transform: translateY(-6px) rotate(-45deg); width: 100%; }

.by-nav {
  display: flex;
  align-items: center;
  gap: 20px;
}

.by-nav__list {
  display: flex;
  align-items: center;
  gap: 2px;
}

.by-nav__link {
  display: block;
  padding: 9px 13px;
  border: 1.5px solid transparent;
  border-radius: 11px;
  font-size: 15px;
  font-weight: 600;
  color: rgba(217, 226, 236, .86);
  transition: color .2s ease, background-color .2s ease, border-color .2s ease, box-shadow .2s ease;
}

.by-nav__link:hover {
  color: var(--by-sand);
  background: rgba(0, 212, 255, .09);
  border-color: var(--by-line);
}

.by-nav__link[aria-current="page"] {
  color: var(--by-ink);
  background: var(--by-grad-signal);
  border-color: rgba(127, 231, 255, .7);
  box-shadow: 0 6px 18px rgba(0, 212, 255, .26);
}

.by-nav__cta {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 11px 18px;
  border: 2px solid #FF9678;
  border-radius: 13px;
  background: var(--by-coral);
  color: #2A0D05;
  font-family: var(--by-font-head);
  font-size: 14.5px;
  font-weight: 800;
  letter-spacing: .03em;
  box-shadow: 4px 4px 0 rgba(7, 19, 31, .55);
  transition: transform .2s ease, box-shadow .2s ease, background-color .2s ease;
}

.by-nav__cta:hover {
  color: #2A0D05;
  background: #FF8564;
  transform: translate(-1px, -3px);
  box-shadow: 7px 8px 0 rgba(7, 19, 31, .6);
}

.by-header__progress {
  position: absolute;
  left: 0;
  right: 0;
  bottom: -2px;
  z-index: 2;
  height: 3px;
  background: rgba(127, 231, 255, .13);
  overflow: hidden;
}

.by-header__progress-bar {
  display: block;
  height: 100%;
  width: 100%;
  transform: scaleX(0);
  transform-origin: 0 50%;
  background: linear-gradient(90deg, #1B6B8C 0%, #00D4FF 55%, #FF6B4A 100%);
  transition: transform .12s linear;
}

/* ---------- 页脚 ---------- */

.by-footer {
  position: relative;
  overflow: hidden;
  color: var(--by-pearl);
  background: linear-gradient(180deg, #07131F 0%, #0A2540 44%, #0E3A5C 100%);
  border-top: 3px solid var(--by-line-strong);
}

.by-footer__glow {
  position: absolute;
  inset: -34% -10% auto -10%;
  height: 68%;
  pointer-events: none;
  background:
    radial-gradient(58% 58% at 18% 42%, rgba(0, 212, 255, .20), rgba(0, 212, 255, 0) 70%),
    radial-gradient(48% 48% at 84% 22%, rgba(255, 107, 74, .15), rgba(255, 107, 74, 0) 72%);
}

.by-footer__inner {
  position: relative;
  z-index: 1;
  width: min(100%, var(--by-shell));
  margin: 0 auto;
  padding: clamp(46px, 7vw, 84px) var(--by-gutter) 42px;
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1.55fr);
  gap: clamp(32px, 5vw, 72px);
}

.by-footer__brand { min-width: 0; }

.by-footer__logo {
  font-family: var(--by-font-head);
  font-size: clamp(24px, 3.2vw, 34px);
  font-weight: 800;
  letter-spacing: .05em;
  color: var(--by-sand);
  margin-bottom: 8px;
}

.by-footer__tagline {
  font-size: 14px;
  letter-spacing: .05em;
  color: var(--by-electric-soft);
}

.by-footer__facts {
  display: grid;
  gap: 12px;
  margin: 24px 0 26px;
}

.by-footer__fact {
  display: grid;
  grid-template-columns: 84px minmax(0, 1fr);
  gap: 12px;
  align-items: baseline;
  padding-bottom: 11px;
  border-bottom: 1px dashed rgba(127, 231, 255, .16);
}

.by-footer__fact dt {
  font-family: var(--by-font-mono);
  font-size: 11.5px;
  letter-spacing: .14em;
  color: rgba(127, 231, 255, .78);
}

.by-footer__fact dd {
  font-size: 14.5px;
  line-height: 1.6;
  color: rgba(217, 226, 236, .86);
  word-break: break-word;
}

.by-footer__grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 30px 28px;
  align-content: start;
}

.by-footer__col { min-width: 0; }

.by-footer__col-title {
  position: relative;
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 2px solid var(--by-line);
  font-family: var(--by-font-head);
  font-size: 13.5px;
  font-weight: 800;
  letter-spacing: .16em;
  color: var(--by-sand);
}

.by-footer__col-title::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: -2px;
  width: 38px;
  height: 2px;
  background: var(--by-coral);
}

.by-footer__list { display: grid; gap: 11px; }

.by-footer__item {
  font-size: 14.5px;
  line-height: 1.6;
  color: rgba(217, 226, 236, .78);
  word-break: break-word;
}

.by-footer__link {
  color: var(--by-electric-soft);
  border-bottom: 1.5px solid rgba(0, 212, 255, .28);
}

.by-footer__link:hover {
  color: var(--by-electric);
  border-color: var(--by-coral);
}

.by-footer__base {
  position: relative;
  z-index: 1;
  width: min(100%, var(--by-shell));
  margin: 0 auto;
  padding: 20px var(--by-gutter) 34px;
  border-top: 1px solid rgba(127, 231, 255, .16);
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 12px 26px;
  font-size: 13.5px;
  color: rgba(217, 226, 236, .68);
}

.by-footer__copy { margin: 0; }

.by-footer__base-links {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 22px;
}

.by-footer__base-links .by-footer__link {
  font-size: 13.5px;
  border-bottom-color: transparent;
}

.by-footer__base-links .by-footer__link:hover { border-bottom-color: var(--by-coral); }

/* ---------- 通用按钮 ---------- */

.by-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 9px;
  padding: 13px 22px;
  border: 2px solid transparent;
  border-radius: var(--by-radius-m);
  font-family: var(--by-font-head);
  font-size: 15px;
  font-weight: 800;
  letter-spacing: .03em;
  cursor: pointer;
  transition: transform .2s ease, box-shadow .2s ease, background-color .2s ease, color .2s ease;
}

.by-btn--coral {
  background: var(--by-coral);
  color: #2A0D05;
  border-color: #FF9678;
  box-shadow: 5px 5px 0 rgba(7, 19, 31, .6);
}

.by-btn--coral:hover {
  color: #2A0D05;
  background: #FF8564;
  transform: translate(-1px, -3px);
  box-shadow: 8px 9px 0 rgba(7, 19, 31, .62);
}

.by-btn--ghost {
  background: transparent;
  color: var(--by-electric-soft);
  border-color: var(--by-line-strong);
  box-shadow: 5px 5px 0 rgba(7, 19, 31, .38);
}

.by-btn--ghost:hover {
  color: var(--by-ink);
  background: var(--by-electric-soft);
  transform: translate(-1px, -3px);
  box-shadow: 8px 9px 0 rgba(7, 19, 31, .45);
}

.by-btn--sm {
  padding: 9px 16px;
  font-size: 13.5px;
  border-radius: 11px;
}

/* ---------- 面包屑 ---------- */

.by-crumb {
  width: min(100%, var(--by-shell));
  margin: 0 auto;
  padding: 22px var(--by-gutter) 0;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  font-family: var(--by-font-mono);
  font-size: 12px;
  letter-spacing: .1em;
  text-transform: uppercase;
  color: rgba(217, 226, 236, .6);
}

.by-crumb a { color: rgba(127, 231, 255, .85); }
.by-crumb a:hover { color: var(--by-electric); }

.by-crumb__sep { color: rgba(255, 107, 74, .8); }

.by-crumb__item[aria-current="page"] { color: var(--by-sand); }

/* ---------- 章节与标题 ---------- */

.by-section { padding: clamp(52px, 8vw, 104px) 0; }
.by-section--tight { padding: clamp(34px, 5vw, 60px) 0; }

.by-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 16px;
  font-family: var(--by-font-mono);
  font-size: 12px;
  letter-spacing: .24em;
  text-transform: uppercase;
  color: var(--by-electric);
}

.by-eyebrow::before {
  content: "";
  width: 28px;
  height: 2px;
  background: linear-gradient(90deg, var(--by-coral), var(--by-electric));
}

.by-section__head {
  max-width: 62ch;
  margin-bottom: clamp(24px, 4vw, 44px);
}

.by-section__title { margin-bottom: 14px; }

.by-section__lede {
  font-size: 17.5px;
  line-height: 1.75;
  color: rgba(217, 226, 236, .82);
}

/* ---------- 卡片 ---------- */

.by-card {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 14px;
  padding: clamp(20px, 3vw, 30px);
  border: 2px solid var(--by-line);
  border-radius: var(--by-radius-l);
  background: var(--by-grad-panel);
  box-shadow: var(--by-shadow-card);
  color: var(--by-pearl);
  transition: transform .28s ease, box-shadow .28s ease, border-color .28s ease;
}

.by-card:hover {
  transform: translate(-2px, -6px);
  box-shadow: var(--by-shadow-card-hover);
  border-color: var(--by-line-strong);
}

.by-card__title {
  font-size: 20px;
  color: var(--by-sand);
}

.by-card__text {
  font-size: 15.5px;
  line-height: 1.72;
  color: rgba(217, 226, 236, .78);
}

.by-card__foot {
  margin-top: auto;
  padding-top: 13px;
  border-top: 1px dashed rgba(127, 231, 255, .22);
  font-family: var(--by-font-mono);
  font-size: 12px;
  letter-spacing: .09em;
  color: rgba(127, 231, 255, .82);
}

.by-card--light {
  background: var(--by-sand);
  color: var(--by-ink);
  border-color: rgba(10, 37, 64, .2);
  box-shadow: 10px 10px 0 rgba(7, 19, 31, .2);
}

.by-card--light .by-card__title { color: var(--by-ink); }
.by-card--light .by-card__text { color: rgba(7, 19, 31, .78); }
.by-card--light .by-card__foot {
  color: rgba(10, 37, 64, .7);
  border-top-color: rgba(10, 37, 64, .16);
}

/* ---------- 标签 ---------- */

.by-tag {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  padding: 5px 12px;
  border: 1.5px solid var(--by-line);
  border-radius: 999px;
  background: rgba(0, 212, 255, .08);
  font-family: var(--by-font-mono);
  font-size: 11.5px;
  letter-spacing: .1em;
  color: var(--by-electric-soft);
  white-space: nowrap;
}

.by-tag--coral {
  border-color: rgba(255, 107, 74, .55);
  background: rgba(255, 107, 74, .13);
  color: #FFB6A2;
}

.by-tag--solid {
  border-color: var(--by-electric);
  background: var(--by-electric);
  color: var(--by-ink);
  font-weight: 700;
}

.by-tag--muted {
  border-color: rgba(217, 226, 236, .22);
  background: rgba(217, 226, 236, .07);
  color: rgba(217, 226, 236, .72);
}

/* ---------- 数字块 ---------- */

.by-num {
  padding: 20px 22px;
  border: 2px solid var(--by-line);
  border-radius: 16px;
  background: linear-gradient(150deg, rgba(0, 212, 255, .13) 0%, rgba(14, 58, 92, .52) 100%);
  box-shadow: 6px 6px 0 rgba(7, 19, 31, .5);
}

.by-num__value {
  display: block;
  font-family: var(--by-font-mono);
  font-variant-numeric: tabular-nums;
  font-size: clamp(30px, 4.4vw, 52px);
  font-weight: 700;
  line-height: 1;
  color: var(--by-electric);
}

.by-num__label {
  display: block;
  margin-top: 9px;
  font-size: 13.5px;
  letter-spacing: .05em;
  color: rgba(217, 226, 236, .78);
}

.by-num--coral .by-num__value { color: var(--by-coral); }

/* ---------- 网格 ---------- */

.by-grid { display: grid; gap: clamp(18px, 2.6vw, 28px); }
.by-grid--2 { grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); }
.by-grid--3 { grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); }
.by-grid--4 { grid-template-columns: repeat(auto-fit, minmax(196px, 1fr)); }
.by-grid--auto { grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); }

/* ---------- 正文排版 ---------- */

.by-prose {
  max-width: 44em;
  font-size: 17px;
  line-height: 1.78;
  color: rgba(217, 226, 236, .86);
}

.by-prose > * + * { margin-top: 1.1em; }
.by-prose h2 { margin-top: 1.9em; }
.by-prose h3 { margin-top: 1.55em; }
.by-prose strong { color: var(--by-sand); }

.by-prose a { border-bottom: 1.5px solid rgba(0, 212, 255, .5); }
.by-prose a:hover { border-color: var(--by-coral); }

.by-prose ul, .by-prose ol { display: grid; gap: 10px; }

.by-prose ul li {
  position: relative;
  padding-left: 22px;
}

.by-prose ul li::before {
  content: "";
  position: absolute;
  left: 0;
  top: .72em;
  width: 9px;
  height: 9px;
  border-radius: 3px;
  background: var(--by-grad-signal);
}

.by-prose ol { counter-reset: by-ol; }

.by-prose ol li {
  position: relative;
  padding-left: 30px;
  counter-increment: by-ol;
}

.by-prose ol li::before {
  content: counter(by-ol, decimal-leading-zero);
  position: absolute;
  left: 0;
  top: .1em;
  font-family: var(--by-font-mono);
  font-size: 12.5px;
  color: var(--by-coral);
}

.by-prose code {
  padding: 2px 6px;
  border: 1px solid var(--by-line);
  border-radius: 6px;
  background: rgba(0, 212, 255, .12);
  font-family: var(--by-font-mono);
  font-size: .92em;
  color: var(--by-electric-soft);
}

/* ---------- 图片容器基础规则（页面阶段再放图） ---------- */

.by-media {
  position: relative;
  display: block;
  overflow: hidden;
  border: 2px solid var(--by-line);
  border-radius: var(--by-radius-l);
  background: linear-gradient(140deg, #0E3A5C 0%, #0A2540 58%, #07131F 100%);
  box-shadow: var(--by-shadow-card);
  isolation: isolate;
}

.by-media::after {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 1;
  pointer-events: none;
  background:
    radial-gradient(90% 70% at 14% 6%, rgba(0, 212, 255, .26), rgba(0, 212, 255, 0) 62%),
    radial-gradient(70% 60% at 88% 94%, rgba(255, 107, 74, .18), rgba(255, 107, 74, 0) 66%);
}

.by-media > img,
.by-media > svg,
.by-media > video,
.by-media > picture > img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.by-media--16x9 { aspect-ratio: 16 / 9; }
.by-media--4x3 { aspect-ratio: 4 / 3; }
.by-media--1x1 { aspect-ratio: 1 / 1; }
.by-media--wide { aspect-ratio: 21 / 9; }

.by-media__caption {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 2;
  margin: 0;
  padding: 16px 18px 14px;
  background: linear-gradient(0deg, rgba(7, 19, 31, .94) 0%, rgba(7, 19, 31, 0) 100%);
  font-family: var(--by-font-mono);
  font-size: 12px;
  letter-spacing: .08em;
  color: var(--by-electric-soft);
}

/* ---------- 显现动效 ---------- */

.by-js [data-reveal] {
  opacity: 0;
  transform: translate3d(0, 20px, 0);
  transition: opacity .62s cubic-bezier(.2, .7, .3, 1), transform .62s cubic-bezier(.2, .7, .3, 1);
}

.by-js [data-reveal].is-visible {
  opacity: 1;
  transform: none;
}

/* ---------- 响应式 ---------- */

@media (max-width: 1180px) {
  .by-status__text { display: none; }
  .by-nav { gap: 14px; }
  .by-nav__link { padding: 8px 10px; font-size: 14px; }
}

@media (max-width: 1024px) {
  .by-footer__inner {
    grid-template-columns: 1fr;
    gap: 42px;
  }
}

@media (max-width: 920px) {
  :root { --by-header-h: 64px; }

  .by-navtoggle { display: inline-flex; }

  .by-nav {
    position: fixed;
    top: var(--by-header-h);
    left: 0;
    right: 0;
    z-index: 110;
    display: block;
    max-height: 0;
    overflow: hidden;
    visibility: hidden;
    padding: 0 var(--by-gutter);
    background: linear-gradient(180deg, #0A2540 0%, #0E3A5C 100%);
    border-bottom: 2px solid var(--by-line-strong);
    box-shadow: 0 26px 44px rgba(3, 11, 19, .58);
    transition: max-height .34s ease, visibility .34s ease, padding-bottom .34s ease;
  }

  .by-nav[data-open] {
    max-height: min(80vh, 620px);
    overflow-y: auto;
    visibility: visible;
    padding-bottom: 26px;
  }

  .by-nav__list {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: 10px 0 4px;
  }

  .by-nav__item { border-bottom: 1px solid rgba(127, 231, 255, .14); }

  .by-nav__link {
    padding: 15px 4px;
    border: 0;
    border-radius: 0;
    background: none;
    font-size: 17px;
    color: var(--by-pearl);
  }

  .by-nav__link:hover {
    background: none;
    border-color: transparent;
    color: var(--by-electric-soft);
  }

  .by-nav__link[aria-current="page"] {
    background: none;
    color: var(--by-electric);
    box-shadow: none;
  }

  .by-nav__link[aria-current="page"]::before {
    content: "";
    display: inline-block;
    width: 8px;
    height: 8px;
    margin-right: 10px;
    border-radius: 50%;
    background: var(--by-coral);
    box-shadow: 0 0 10px var(--by-coral);
    vertical-align: middle;
  }

  .by-nav__cta {
    width: 100%;
    margin-top: 18px;
    padding: 14px 18px;
  }
}

@media (max-width: 640px) {
  body { font-size: 16.5px; }

  .by-brand__mark { width: 36px; height: 36px; border-radius: 13px 13px 13px 4px; }
  .by-brand__name { font-size: 17px; letter-spacing: .05em; }
  .by-brand__meta { display: none; }
  .by-header__brand-zone { gap: 12px; }

  .by-footer__fact { grid-template-columns: 1fr; gap: 4px; }
  .by-footer__base { flex-direction: column; align-items: flex-start; }
  .by-footer__base-links { gap: 8px 18px; }
}

/* ---------- 动效降级 ---------- */

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }

  *, *::before, *::after {
    animation-duration: .001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .001ms !important;
    transition-delay: 0ms !important;
  }

  .by-status__dot { animation: none; }

  .by-js [data-reveal] {
    opacity: 1 !important;
    transform: none !important;
  }

  .by-card:hover,
  .by-btn:hover,
  .by-nav__cta:hover {
    transform: none;
  }
}