:root {
  --ink: #142330;
  --muted: #536879;
  --blue-900: #082f55;
  --blue-800: #0a3d6b;
  --blue-700: #1a5a8c;
  --blue-500: #3a7bb5;
  --blue-100: #dfeefa;
  --line: rgba(10, 61, 107, .16);
  --paper: rgba(255, 255, 255, .93);
  --paper-strong: rgba(255, 255, 255, .975);
  --shadow: 0 22px 70px rgba(8, 47, 85, .10);
  --radius: 18px;
  --content: 980px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 100px; }
body {
  margin: 0;
  min-width: 320px;
  color: var(--ink);
  background: #eef4f8;
  font-family: Inter, ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", Arial, sans-serif;
  font-size: 17px;
  line-height: 1.78;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
body::before {
  content: "";
  position: fixed;
  inset: 0;
  z-index: -2;
  background-image: url("hteam-brush-section.587de3a2a2.webp");
  background-repeat: no-repeat;
  background-attachment: fixed;
  background-position: center 47%;
  background-size: min(78vw, 1060px) auto;
  opacity: .08;
  pointer-events: none;
}
body::after {
  content: "";
  position: fixed;
  inset: 0;
  z-index: -1;
  background:
    linear-gradient(180deg, rgba(247,250,252,.92) 0%, rgba(238,244,248,.84) 48%, rgba(247,250,252,.94) 100%),
    radial-gradient(circle at 15% 12%, rgba(58,123,181,.09), transparent 33%),
    radial-gradient(circle at 88% 72%, rgba(10,61,107,.07), transparent 35%);
  pointer-events: none;
}

::selection { background: rgba(58, 123, 181, .25); }
a { color: inherit; }
img { max-width: 100%; }

.reading-progress {
  position: fixed;
  inset: 0 0 auto 0;
  z-index: 100;
  height: 3px;
  background: rgba(10, 61, 107, .08);
}
.reading-progress span {
  display: block;
  width: 0;
  height: 100%;
  background: linear-gradient(90deg, var(--blue-500), var(--blue-800));
  transition: width .08s linear;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 90;
  border-bottom: 1px solid rgba(10, 61, 107, .12);
  background: rgba(255, 255, 255, .87);
  backdrop-filter: blur(18px) saturate(145%);
  -webkit-backdrop-filter: blur(18px) saturate(145%);
}
.header-inner {
  width: min(calc(100% - 40px), 1180px);
  min-height: 78px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: 26px;
}
.brand {
  display: inline-flex;
  flex: 0 0 auto;
  align-items: center;
  min-height: 48px;
}
.brand img {
  display: block;
  width: auto;
  height: 54px;
  object-fit: contain;
}
.primary-nav {
  margin-left: auto;
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: 2px;
}
.primary-nav a {
  position: relative;
  min-height: 44px;
  padding: 10px 11px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  color: #385268;
  font-size: 13px;
  font-weight: 620;
  letter-spacing: .02em;
  text-decoration: none;
  white-space: nowrap;
  border-radius: 9px;
  transition: color .18s ease, background .18s ease;
}
.primary-nav a:hover,
.primary-nav a:focus-visible,
.primary-nav a.is-active {
  color: var(--blue-800);
  background: rgba(58, 123, 181, .10);
  outline: none;
}
.primary-nav a.is-active::after {
  content: "";
  position: absolute;
  left: 13px;
  right: 13px;
  bottom: 4px;
  height: 2px;
  border-radius: 2px;
  background: var(--blue-500);
}
.menu-button { display: none; }

.page-shell {
  width: min(calc(100% - 40px), var(--content));
  margin: 0 auto;
  padding: 56px 0 72px;
}
.page-kicker {
  margin: 0 4px 22px;
  display: flex;
  align-items: center;
  gap: 14px;
  color: var(--blue-700);
  font-size: 11px;
  font-weight: 760;
  letter-spacing: .17em;
}
.page-kicker i {
  height: 1px;
  flex: 1;
  background: linear-gradient(90deg, rgba(10,61,107,.35), rgba(10,61,107,.04));
}
.letter {
  display: grid;
  gap: 26px;
}
.letter-section {
  --section-wash: linear-gradient(135deg, rgba(255,255,255,.965), rgba(242,248,252,.95));
  position: relative;
  overflow: hidden;
  padding: clamp(30px, 4.5vw, 52px) clamp(24px, 5vw, 60px);
  border: 1px solid rgba(10, 61, 107, .13);
  border-radius: var(--radius);
  background-color: rgba(255,255,255,.96);
  background-image: var(--section-wash), url("hteam-brush-section.587de3a2a2.webp");
  background-repeat: no-repeat, no-repeat;
  background-position: center, center;
  background-size: cover, contain;
  box-shadow: var(--shadow);
  scroll-margin-top: 104px;
}
.letter-section::before {
  content: "";
  position: absolute;
  inset: 0 auto 0 0;
  width: 4px;
  background: linear-gradient(180deg, var(--blue-500), rgba(58,123,181,.16));
}
.letter-section:nth-child(even) {
  --section-wash: linear-gradient(135deg, rgba(247,251,254,.97), rgba(238,246,251,.955));
  background-color: rgba(247,251,254,.96);
}
.letter-section--intro {
  --section-wash: linear-gradient(135deg, rgba(255,255,255,.97), rgba(237,246,252,.95));
  padding-top: clamp(34px, 6vw, 66px);
}
.letter-section--intro::after {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  width: 220px;
  height: 220px;
  background: linear-gradient(135deg, transparent 49.6%, rgba(58,123,181,.12) 50%, rgba(58,123,181,.12) 50.5%, transparent 51%);
  opacity: .65;
  pointer-events: none;
}
.letter-section--closing {
  --section-wash: linear-gradient(135deg, rgba(255,255,255,.975), rgba(229,241,249,.96));
  background-color: rgba(247, 251, 254, .97);
  color: var(--ink);
  border-color: rgba(10, 61, 107, .16);
}
.letter-section--closing::before {
  background: linear-gradient(180deg, var(--blue-500), rgba(58,123,181,.2));
}
.letter-section--closing strong { color: var(--blue-900); }

.intro-rule,
.section-heading-row {
  position: relative;
  z-index: 1;
  margin-bottom: 24px;
}
.intro-rule {
  display: flex;
  align-items: center;
  gap: 12px;
  color: var(--blue-700);
  font-size: 11px;
  font-weight: 760;
  letter-spacing: .18em;
}
.intro-rule i {
  width: 54px;
  height: 1px;
  background: var(--blue-500);
}
.section-heading-row {
  display: grid;
  grid-template-columns: 45px minmax(0, 1fr);
  align-items: center;
  gap: 16px;
}
.section-index {
  color: var(--blue-500);
  font-size: 12px;
  font-weight: 760;
  letter-spacing: .12em;
}
.section-heading-row h2 {
  margin: 0;
  color: var(--blue-900);
  font-size: clamp(22px, 3.1vw, 27px);
  line-height: 1.35;
  font-weight: 400;
  letter-spacing: .01em;
}
.section-heading-row h2::after {
  content: "";
  display: block;
  width: min(190px, 40%);
  height: 2px;
  margin-top: 14px;
  background: linear-gradient(90deg, var(--blue-500), rgba(58,123,181,0));
}
.section-heading-row--closing { margin-bottom: 12px; }
.closing-rule {
  height: 1px;
  background: linear-gradient(90deg, rgba(10,61,107,.44), rgba(58,123,181,.06));
}
.letter-section--closing .section-index { color: var(--blue-500); }

.section-copy {
  position: relative;
  z-index: 1;
}
.doc-paragraph {
  margin: 0;
  color: var(--ink);
  font-size: 17px;
  line-height: 1.82;
  text-indent: 2em;
  text-align: justify;
  text-justify: inter-ideograph;
  overflow-wrap: anywhere;
}
.doc-paragraph.no-indent {
  text-indent: 0;
}
.doc-paragraph + .doc-paragraph { margin-top: 1.15em; }
.doc-paragraph.lead {
  color: var(--ink);
  font-size: 17px;
  line-height: 1.82;
}
.doc-paragraph.lead::first-letter {
  float: none;
  margin: 0;
  color: inherit;
  font-size: inherit;
  font-weight: inherit;
  line-height: inherit;
}
strong {
  color: var(--blue-900);
  font-weight: 760;
}
.letter-section--closing .doc-paragraph { color: var(--ink); }

.site-footer {
  width: min(calc(100% - 40px), var(--content));
  margin: 0 auto;
  padding: 0 0 42px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 14px;
  color: #577084;
  font-size: 12px;
  letter-spacing: .08em;
}
.site-footer img {
  width: auto;
  height: 30px;
  opacity: .64;
}
.site-footer p { margin: 0; }
.back-to-top {
  position: fixed;
  right: max(18px, env(safe-area-inset-right));
  bottom: max(18px, env(safe-area-inset-bottom));
  z-index: 50;
  width: 46px;
  height: 46px;
  display: grid;
  place-items: center;
  color: #fff;
  background: rgba(10,61,107,.9);
  border: 1px solid rgba(255,255,255,.34);
  border-radius: 50%;
  box-shadow: 0 12px 30px rgba(8,47,85,.22);
  text-decoration: none;
  opacity: 0;
  transform: translateY(8px);
  pointer-events: none;
  transition: opacity .2s ease, transform .2s ease;
}
.back-to-top.is-visible { opacity: 1; transform: none; pointer-events: auto; }
.back-to-top:focus-visible { outline: 3px solid rgba(58,123,181,.4); outline-offset: 3px; }

@media (max-width: 1040px) {
  .primary-nav a { padding-inline: 8px; font-size: 12px; }
  .brand img { height: 48px; }
}

@media (max-width: 860px) {
  html { scroll-padding-top: 86px; }
  body::before { background-size: 92vw auto; opacity: .06; }
  body::after { background-color: rgba(246,249,251,.22); }
  .header-inner { min-height: 70px; }
  .brand img { height: 44px; max-width: 225px; }
  .menu-button {
    margin-left: auto;
    min-width: 82px;
    min-height: 44px;
    padding: 8px 12px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 9px;
    color: var(--blue-800);
    background: rgba(58,123,181,.08);
    border: 1px solid rgba(10,61,107,.14);
    border-radius: 10px;
    font: inherit;
    font-size: 14px;
    font-weight: 680;
  }
  .menu-icon { width: 17px; display: grid; gap: 4px; }
  .menu-icon i { display: block; height: 1.5px; background: currentColor; border-radius: 2px; transition: transform .2s ease, opacity .2s ease; }
  .menu-button[aria-expanded="true"] .menu-icon i:nth-child(1) { transform: translateY(5.5px) rotate(45deg); }
  .menu-button[aria-expanded="true"] .menu-icon i:nth-child(2) { opacity: 0; }
  .menu-button[aria-expanded="true"] .menu-icon i:nth-child(3) { transform: translateY(-5.5px) rotate(-45deg); }
  .primary-nav {
    position: absolute;
    top: calc(100% + 1px);
    left: 20px;
    right: 20px;
    margin: 0;
    padding: 10px;
    display: grid;
    grid-template-columns: repeat(2, minmax(0,1fr));
    gap: 4px;
    background: rgba(255,255,255,.98);
    border: 1px solid rgba(10,61,107,.13);
    border-radius: 0 0 14px 14px;
    box-shadow: 0 18px 38px rgba(8,47,85,.14);
    transform-origin: top;
    transform: scaleY(.94) translateY(-8px);
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
    transition: opacity .18s ease, transform .18s ease, visibility .18s;
  }
  .primary-nav.is-open { transform: none; opacity: 1; visibility: visible; pointer-events: auto; }
  .primary-nav a { justify-content: flex-start; padding: 10px 12px; font-size: 13px; }
  .primary-nav a.is-active::after { display: none; }
  .page-shell { padding-top: 36px; }
}

@media (max-width: 600px) {
  body {
    font-size: 16px;
    line-height: 1.72;
  }
  body::before {
    background-position: center 36%;
    background-size: 96vw auto;
    opacity: .045;
  }
  body::after {
    background: linear-gradient(180deg, rgba(248,250,252,.94), rgba(239,245,249,.91) 45%, rgba(248,250,252,.95));
  }
  .header-inner,
  .page-shell,
  .site-footer { width: min(calc(100% - 28px), var(--content)); }
  .header-inner { min-height: 66px; gap: 12px; }
  .brand img { height: 38px; max-width: 185px; }
  .menu-button { min-width: 76px; min-height: 44px; padding-inline: 10px; }
  .primary-nav { left: 14px; right: 14px; }
  .page-shell { padding: 28px 0 54px; }
  .page-kicker { margin-bottom: 16px; gap: 8px; font-size: 9px; letter-spacing: .11em; }
  .page-kicker span:last-child { display: none; }
  .letter { gap: 16px; }
  .letter-section {
    --section-wash: linear-gradient(135deg, rgba(255,255,255,.982), rgba(241,248,252,.972));
    padding: 28px 22px 30px;
    border-radius: 14px;
    background-color: var(--paper-strong);
    background-image: var(--section-wash), url("hteam-brush-section.587de3a2a2.webp");
    background-repeat: no-repeat, no-repeat;
    background-position: center, center;
    background-size: cover, contain;
    box-shadow: 0 14px 42px rgba(8,47,85,.09);
    scroll-margin-top: 82px;
  }
  .letter-section:nth-child(even) {
    --section-wash: linear-gradient(135deg, rgba(248,251,254,.985), rgba(237,246,251,.975));
    background-color: rgba(248,251,254,.975);
  }
  .letter-section--intro { padding-top: 32px; }
  .letter-section--intro::after { width: 130px; height: 130px; }
  .section-heading-row { grid-template-columns: 34px minmax(0,1fr); gap: 10px; margin-bottom: 19px; }
  .section-heading-row h2 { font-size: 22px; }
  .section-heading-row h2::after { margin-top: 10px; }
  .section-index { font-size: 10px; }
  .intro-rule { margin-bottom: 18px; font-size: 9px; }
  .doc-paragraph,
  .doc-paragraph.lead {
    font-size: 16px;
    line-height: 1.82;
    text-align: left;
  }
  .doc-paragraph + .doc-paragraph { margin-top: 1.05em; }
  .doc-paragraph.lead::first-letter { font-size: inherit; }
  .site-footer { padding-bottom: 34px; flex-direction: column; gap: 5px; }
  .site-footer img { height: 26px; }
  .back-to-top { width: 44px; height: 44px; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { transition-duration: .01ms !important; animation-duration: .01ms !important; animation-iteration-count: 1 !important; }
}

@media print {
  body::before, body::after, .site-header, .reading-progress, .back-to-top, .page-kicker, .site-footer { display: none !important; }
  body { background: #fff; font-size: 11pt; }
  .page-shell { width: 100%; padding: 0; }
  .letter { gap: 12pt; }
  .letter-section { padding: 18pt; box-shadow: none; break-inside: avoid; background: #fff !important; }
  .letter-section--closing { color: var(--ink); border-color: var(--line); }
  .letter-section--closing .doc-paragraph { color: var(--ink); }
}