:root {
  --color-ink: #2C2419;
  --color-tea: #3D5C4A;
  --color-warm: #F5F0E8;
  --color-amber: #C8923E;
  --color-tea-deep: #2a4538;

  --font-sans: "PingFang SC", "Hiragino Sans GB", "Noto Sans SC", "Microsoft YaHei", sans-serif;
  --font-serif: "Songti SC", "Noto Serif SC", "STSong", "SimSun", serif;

  --space-xs: 0.5rem;
  --space-sm: 0.75rem;
  --space-md: 1.25rem;
  --space-lg: 2rem;
  --space-xl: 3rem;
  --space-2xl: 4.5rem;

  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: 1.125rem;
  --text-xl: 1.5rem;
  --text-2xl: clamp(1.65rem, 4vw, 2.25rem);

  --rail-width: 3.25rem;
  --content-max: 52rem;
  --top-bar-h: 3.5rem;
}

#about,
#services,
#advantages {
  scroll-margin-top: calc(var(--top-bar-h) + 0.5rem);
}

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

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: var(--text-base);
  line-height: 1.65;
  color: var(--color-ink);
  background-color: var(--color-warm);
}

a {
  color: var(--color-tea);
}

a:focus-visible,
button:focus-visible {
  outline: 2px solid var(--color-amber);
  outline-offset: 2px;
}

.top-bar {
  position: sticky;
  top: 0;
  z-index: 40;
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: var(--top-bar-h);
  padding: var(--space-xs) var(--space-md);
  background: var(--color-ink);
  color: var(--color-warm);
}

.top-bar__name {
  margin: 0;
  font-size: var(--text-sm);
  font-weight: 600;
  letter-spacing: 0.02em;
}

.menu-toggle {
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 2.5rem;
  height: 2.5rem;
  padding: 0;
  border: 1px solid rgba(245, 240, 232, 0.35);
  border-radius: 2px;
  background: transparent;
  cursor: pointer;
}

.menu-toggle__line {
  display: block;
  width: 1.25rem;
  height: 2px;
  margin: 0 auto;
  background: var(--color-warm);
}

.side-rail {
  position: fixed;
  top: var(--top-bar-h);
  left: 0;
  z-index: 30;
  width: min(85vw, 16rem);
  height: calc(100vh - var(--top-bar-h));
  padding: var(--space-lg) var(--space-md);
  background: var(--color-tea-deep);
  color: var(--color-warm);
  transform: translateX(-105%);
  transition: transform 0.28s ease;
}

.side-rail.is-open {
  transform: translateX(0);
}

.side-rail__line {
  position: absolute;
  left: 1.35rem;
  top: var(--space-lg);
  width: 4px;
  height: calc(100% - var(--space-2xl));
  pointer-events: none;
}

.side-rail__pulse-path {
  stroke: var(--color-amber);
  stroke-width: 2;
  stroke-dasharray: 8 14;
  animation: rail-pulse 2.4s ease-in-out infinite;
}

@keyframes rail-pulse {
  0%, 100% { stroke-opacity: 0.35; stroke-dashoffset: 0; }
  50% { stroke-opacity: 1; stroke-dashoffset: -22; }
}

.side-rail__nav {
  display: flex;
  flex-direction: column;
  gap: var(--space-lg);
  margin-left: 0.25rem;
}

.side-rail__link {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  text-decoration: none;
  color: rgba(245, 240, 232, 0.75);
  font-size: var(--text-sm);
  transition: color 0.2s ease;
}

.side-rail__link:hover,
.side-rail__link.is-active {
  color: var(--color-warm);
}

.side-rail__dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  border: 2px solid var(--color-amber);
  background: transparent;
  flex-shrink: 0;
  transition: transform 0.25s ease, background 0.25s ease;
}

.side-rail__link.is-active .side-rail__dot {
  background: var(--color-amber);
  animation: dot-pulse 1.8s ease-in-out infinite;
}

@keyframes dot-pulse {
  0%, 100% { transform: scale(1); box-shadow: 0 0 0 0 rgba(200, 146, 62, 0.45); }
  50% { transform: scale(1.15); box-shadow: 0 0 0 6px rgba(200, 146, 62, 0); }
}

.content {
  padding: var(--space-md);
  padding-bottom: var(--space-2xl);
}

.section-title {
  margin: 0 0 var(--space-lg);
  font-family: var(--font-serif);
  font-size: var(--text-xl);
  font-weight: 600;
  color: var(--color-tea);
}

.section-reveal {
  opacity: 0;
  transform: translate(12px, 18px) rotate(0.4deg);
  transition: opacity 0.65s ease, transform 0.65s cubic-bezier(0.22, 1, 0.36, 1);
}

.section-reveal.is-visible {
  opacity: 1;
  transform: translate(0, 0) rotate(0);
}

.hero {
  position: relative;
  display: flex;
  flex-direction: column;
  margin-bottom: var(--space-2xl);
  overflow: hidden;
  background: var(--color-tea);
}

.hero__text {
  order: 2;
  position: relative;
  z-index: 2;
  padding: var(--space-lg) var(--space-md) var(--space-lg);
  background: linear-gradient(145deg, var(--color-warm) 0%, rgba(245, 240, 232, 0.98) 100%);
}

.hero__text::before {
  content: "";
  position: absolute;
  top: -1.75rem;
  left: 0;
  right: 0;
  height: 1.75rem;
  background: inherit;
  clip-path: polygon(0 100%, 100% 0, 100% 100%);
  pointer-events: none;
  z-index: -1;
}

.hero__hook {
  margin: 0 0 var(--space-sm);
  font-size: var(--text-sm);
  color: var(--color-tea);
  letter-spacing: 0.04em;
}

.hero__claim {
  margin: 0 0 var(--space-md);
  font-family: var(--font-serif);
  font-size: var(--text-2xl);
  line-height: 1.35;
  color: var(--color-ink);
  max-width: 14em;
}

.hero__sub {
  margin: 0 0 var(--space-lg);
  font-size: var(--text-sm);
  max-width: 28em;
  color: rgba(44, 36, 25, 0.88);
}

.hero__actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
}

.btn {
  display: inline-block;
  padding: 0.55rem 1.1rem;
  font-size: var(--text-sm);
  text-decoration: none;
  border-radius: 2px;
  border: 1px solid var(--color-tea);
  transition: background 0.2s ease, color 0.2s ease;
}

.btn--solid {
  background: var(--color-tea);
  color: var(--color-warm);
}

.btn--solid:hover {
  background: var(--color-tea-deep);
}

.btn--outline {
  background: transparent;
  color: var(--color-tea);
}

.btn--outline:hover {
  background: rgba(61, 92, 74, 0.08);
}

.hero__visual {
  order: 1;
  position: relative;
  flex: 0 0 auto;
  width: 100%;
  min-height: 240px;
  height: clamp(240px, 52vw, 300px);
  pointer-events: none;
  background: var(--color-tea);
  clip-path: polygon(0 0, 100% 0, 100% 92%, 0 100%);
}

.hero__network {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: contain;
  object-position: center;
  opacity: 0.95;
  animation: net-drift 18s ease-in-out infinite alternate;
}

@keyframes net-drift {
  from { transform: translate(0, 0) scale(1); }
  to { transform: translate(-8px, 6px) scale(1.03); }
}

.about {
  margin-bottom: var(--space-2xl);
}

.about__fold {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0;
  border: 1px solid rgba(44, 36, 25, 0.15);
  background: rgba(255, 255, 255, 0.35);
}

.about__tab {
  margin: 0;
  padding: var(--space-md);
  writing-mode: horizontal-tb;
  font-family: var(--font-serif);
  font-size: var(--text-lg);
  color: var(--color-warm);
  background: var(--color-ink);
  text-align: center;
}

.about__envelope {
  position: relative;
  margin: var(--space-md);
  padding: var(--space-lg) var(--space-md);
  background: var(--color-warm);
  border: 1px solid var(--color-amber);
  border-radius: 0 18px 18px 18px;
  box-shadow: 4px 6px 0 rgba(44, 36, 25, 0.12);
}

.about__envelope::before {
  content: "";
  position: absolute;
  top: -10px;
  left: var(--space-md);
  width: 0;
  height: 0;
  border-left: 12px solid transparent;
  border-right: 12px solid transparent;
  border-bottom: 10px solid var(--color-amber);
}

.about__envelope p {
  margin: 0;
  font-size: var(--text-sm);
  text-align: justify;
}

.services {
  margin-bottom: var(--space-2xl);
}

.services__river {
  list-style: none;
  margin: 0;
  padding: 0 0 0 var(--space-sm);
  border-left: 2px solid var(--color-amber);
}

.service-card {
  position: relative;
  margin: 0 0 var(--space-xl);
  padding: var(--space-md) var(--space-md) var(--space-md) var(--space-lg);
  background: rgba(255, 255, 255, 0.45);
  border-left: 3px solid var(--color-tea);
}

.service-card::before {
  content: "";
  position: absolute;
  left: calc(-1 * var(--space-sm) - 5px);
  top: var(--space-md);
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--color-amber);
  border: 2px solid var(--color-warm);
}

.service-card__title {
  margin: 0 0 var(--space-xs);
  font-family: var(--font-serif);
  font-size: var(--text-lg);
  color: var(--color-tea-deep);
}

.service-card__hook {
  margin: 0 0 var(--space-sm);
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-amber);
}

.service-card__body {
  margin: 0;
  font-size: var(--text-sm);
  color: rgba(44, 36, 25, 0.9);
}

.advantages {
  margin-bottom: var(--space-xl);
}

.advantages__track {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.advantage-card {
  flex: none;
  padding: var(--space-md) var(--space-md) var(--space-md) var(--space-sm);
  background: var(--color-ink);
  color: var(--color-warm);
  border-left: 4px solid var(--color-amber);
}

.advantage-card__title {
  margin: 0 0 var(--space-xs);
  font-size: var(--text-base);
  font-weight: 600;
}

.advantage-card__body {
  margin: 0;
  font-size: var(--text-sm);
  color: rgba(245, 240, 232, 0.88);
}

.site-footer {
  padding: var(--space-md);
  text-align: center;
  font-size: var(--text-sm);
  background: var(--color-ink);
  color: rgba(245, 240, 232, 0.85);
}

.site-footer p {
  margin: 0.35rem 0;
}

.site-footer a {
  color: var(--color-warm);
  text-decoration: underline;
  text-underline-offset: 3px;
}

@media (min-width: 768px) {
  .menu-toggle {
    display: none;
  }

  .side-rail {
    width: var(--rail-width);
    transform: translateX(0);
    padding-top: var(--space-xl);
  }

  .side-rail__label {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
  }

  .content {
    margin-left: var(--rail-width);
    width: calc(100% - var(--rail-width));
    max-width: none;
    padding: var(--space-lg) var(--space-xl);
  }

  .top-bar {
    margin-left: var(--rail-width);
    width: calc(100% - var(--rail-width));
  }

  .site-footer {
    padding-left: calc(var(--rail-width) + var(--space-md));
  }

  .hero {
    display: grid;
    grid-template-columns: 1fr 1.05fr;
    min-height: 420px;
  }

  .hero__text {
    order: unset;
    align-self: stretch;
    display: flex;
    flex-direction: column;
    justify-content: center;
    padding: var(--space-xl);
    max-width: none;
  }

  .hero__text::before {
    top: 0;
    left: auto;
    right: -2.5rem;
    width: 2.75rem;
    height: 100%;
    clip-path: polygon(0 0, 100% 12%, 100% 100%, 0 100%);
  }

  .hero__visual {
    order: unset;
    flex: unset;
    width: auto;
    min-height: 320px;
    height: auto;
    clip-path: polygon(8% 0, 100% 0, 100% 100%, 0 100%);
  }

  .hero__network {
    object-fit: cover;
    object-position: center;
  }

  .about__fold {
    grid-template-columns: auto 1fr;
    align-items: stretch;
  }

  .about__tab {
    writing-mode: vertical-rl;
    text-orientation: mixed;
    letter-spacing: 0.2em;
    padding: var(--space-lg) var(--space-sm);
    min-width: 3rem;
  }

  .about__envelope {
    margin: var(--space-md) var(--space-md) var(--space-md) 0;
  }

  .advantages__track {
    flex-direction: row;
    overflow-x: auto;
    scroll-snap-type: x mandatory;
    scroll-padding-inline: var(--space-md);
    gap: var(--space-md);
    padding-bottom: var(--space-sm);
  }

  .advantage-card {
    scroll-snap-align: start;
    flex: 0 0 calc(33.333% - var(--space-md));
    min-width: 16rem;
  }
}

@media (min-width: 1100px) {
  :root {
    --rail-width: 7.5rem;
  }

  .side-rail__label {
    position: static;
    width: auto;
    height: auto;
    margin: 0;
    overflow: visible;
    clip: auto;
    white-space: nowrap;
    font-size: 0.8125rem;
  }

  .side-rail__link {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.35rem;
  }

  .hero__text {
    padding: var(--space-2xl) var(--space-xl);
  }

  .hero__visual {
    min-height: 380px;
  }

  .service-card--1 {
    width: 96%;
    margin-left: 0;
  }

  .service-card--2 {
    width: 88%;
    margin-left: auto;
    margin-right: 0;
  }

  .service-card--3 {
    width: 78%;
    margin-left: 0;
  }

  .service-card--4 {
    width: 68%;
    margin-left: auto;
    margin-right: 0;
  }
}

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

  .section-reveal {
    opacity: 1;
    transform: none;
    transition: none;
  }

  .hero__network,
  .side-rail__pulse-path,
  .side-rail__link.is-active .side-rail__dot {
    animation: none;
  }
}