:root {
  --color-slate: #2a3238;
  --color-teal: #3d6b5e;
  --color-amber: #c8923a;
  --color-bg: #f0ece6;
  --color-bg-deep: #e4ddd4;
  --color-text: #2a3238;
  --color-text-soft: #4a555c;
  --color-on-dark: #f0ece6;
  --font-serif: "Songti SC", "Noto Serif SC", "STSong", "SimSun", serif;
  --font-sans: "PingFang SC", "Hiragino Sans GB", "Noto Sans SC", "Microsoft YaHei", sans-serif;
  --nav-rail-width: 72px;
  --space-xs: 0.5rem;
  --space-sm: 0.75rem;
  --space-md: 1.25rem;
  --space-lg: 2rem;
  --space-xl: 3rem;
  --text-sm: clamp(0.8125rem, 2.5vw, 0.9375rem);
  --text-base: clamp(0.9375rem, 2.8vw, 1.0625rem);
  --text-lg: clamp(1.125rem, 3.2vw, 1.375rem);
  --text-xl: clamp(1.375rem, 4vw, 1.75rem);
  --text-claim: clamp(1.5rem, 5vw, 2.125rem);
  --max-canvas: 72rem;
  --top-bar-height: 3.25rem;
}

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

html {
  scroll-behavior: smooth;
  overflow-x: hidden;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: var(--text-base);
  line-height: 1.65;
  color: var(--color-text);
  background: var(--color-bg);
  overflow-x: hidden;
}

img,
svg {
  max-width: 100%;
  height: auto;
  display: block;
}

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

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  z-index: 100;
  padding: var(--space-xs) var(--space-sm);
  background: var(--color-slate);
  color: var(--color-on-dark);
}

.skip-link:focus {
  left: var(--space-sm);
}

/* 顶栏（窄屏 / 平板） */
.top-bar {
  position: sticky;
  top: 0;
  z-index: 50;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-xs);
  min-height: var(--top-bar-height);
  padding: var(--space-xs) var(--space-md);
  background: var(--color-slate);
  color: var(--color-on-dark);
}

.top-bar__title {
  margin: 0;
  font-size: var(--text-sm);
  font-weight: 600;
  flex: 1;
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.top-bar__toggle {
  font-family: inherit;
  font-size: var(--text-sm);
  padding: 0.45rem 0.75rem;
  border: 1px solid var(--color-teal);
  background: transparent;
  color: var(--color-on-dark);
  cursor: pointer;
  min-height: 2.75rem;
}

.top-bar__nav {
  width: 100%;
}

.top-bar__nav ul {
  list-style: none;
  margin: 0;
  padding: 0 0 var(--space-sm);
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.top-bar__nav a {
  display: block;
  padding: 0.65rem 0.5rem;
  color: var(--color-on-dark);
  text-decoration: none;
  min-height: 2.75rem;
}

.top-bar__nav a:focus-visible {
  outline: 2px solid var(--color-amber);
  outline-offset: 2px;
}

/* 左侧导航轨（桌面） */
.nav-rail {
  display: none;
}

.canvas {
  width: 100%;
  max-width: 100%;
}

/* 首屏 */
.hero {
  padding: var(--space-lg) var(--space-md) var(--space-xl);
  background: linear-gradient(135deg, var(--color-bg) 0%, var(--color-bg-deep) 100%);
}

.hero__inner {
  display: flex;
  flex-direction: column;
  gap: var(--space-lg);
  max-width: var(--max-canvas);
  margin: 0 auto;
}

.hero__claim {
  margin: 0 0 var(--space-sm);
  font-family: var(--font-serif);
  font-size: var(--text-claim);
  font-weight: 600;
  line-height: 1.35;
  color: var(--color-slate);
}

.hero__hook {
  margin: 0 0 var(--space-sm);
  font-size: var(--text-lg);
  color: var(--color-teal);
  font-weight: 600;
}

.hero__sub {
  margin: 0 0 var(--space-md);
  color: var(--color-text-soft);
  max-width: 36em;
}

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

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.65rem 1.1rem;
  font-size: var(--text-sm);
  text-decoration: none;
  min-height: 2.75rem;
  border: 1px solid transparent;
}

.btn--primary {
  background: var(--color-teal);
  color: var(--color-on-dark);
  border-color: var(--color-teal);
}

.btn--ghost {
  background: transparent;
  color: var(--color-slate);
  border-color: var(--color-slate);
}

.hero__figure {
  margin: 0;
  align-self: center;
  width: min(100%, 12.5rem);
}

.hero__topology {
  width: 100%;
  height: auto;
}

.topology-path {
  stroke-dasharray: 400;
  stroke-dashoffset: 400;
  transition: stroke-dashoffset 1.2s ease-out;
}

.topology-draw-target.is-drawn .topology-path {
  stroke-dashoffset: 0;
}

/* 关于我们 */
.about {
  padding: var(--space-xl) var(--space-md);
  border-top: 3px solid var(--color-slate);
}

.about__heading,
.services__heading,
.advantages__heading {
  margin: 0 0 var(--space-lg);
  font-family: var(--font-serif);
  font-size: var(--text-xl);
  color: var(--color-slate);
  max-width: var(--max-canvas);
  margin-left: auto;
  margin-right: auto;
}

.about__band {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
  max-width: var(--max-canvas);
  margin: 0 auto;
  padding: var(--space-md);
  background: var(--color-slate);
  color: var(--color-on-dark);
  border-left: 4px solid var(--color-amber);
}

.about__labels {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-xs);
}

.about__labels li {
  font-size: var(--text-sm);
  padding: 0.35rem 0.6rem;
  background: var(--color-teal);
  color: var(--color-on-dark);
  white-space: nowrap;
}

.about__body p {
  margin: 0;
  font-size: var(--text-base);
  line-height: 1.75;
}

/* 核心业务 · 书页式四屏 */
.services {
  padding: 0 0 var(--space-xl);
}

.services__heading {
  padding: 0 var(--space-md);
}

.service-page {
  display: flex;
  flex-direction: column;
  gap: var(--space-lg);
  padding: var(--space-xl) var(--space-md);
  width: 100%;
  border-bottom: 1px solid rgba(42, 50, 56, 0.12);
}

.service-page--odd {
  background: var(--color-bg);
}

.service-page--even {
  background: var(--color-bg-deep);
}

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

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

.service-page__body {
  margin: 0;
  color: var(--color-text-soft);
  max-width: 40em;
}

.service-page__viz {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 8rem;
}

.service-svg {
  width: min(100%, 15rem);
  height: auto;
}

/* 核心优势 · 斜切窄带 */
.advantages {
  padding: var(--space-xl) 0 0;
  overflow: hidden;
}

.advantages__heading {
  padding: 0 var(--space-md);
}

.advantage-stripes {
  display: flex;
  flex-direction: column;
}

.advantage-stripe {
  position: relative;
  padding: var(--space-lg) var(--space-md);
  margin-bottom: -0.5rem;
  transform: skewY(-2deg);
  will-change: transform;
}

.advantage-stripe--left {
  background: var(--color-teal);
  color: var(--color-on-dark);
  margin-right: 5%;
}

.advantage-stripe--right {
  background: var(--color-slate);
  color: var(--color-on-dark);
  margin-left: 5%;
  transform: skewY(2deg);
}

.advantage-stripe__inner {
  transform: skewY(2deg);
  max-width: var(--max-canvas);
  margin: 0 auto;
}

.advantage-stripe--right .advantage-stripe__inner {
  transform: skewY(-2deg);
}

.advantage-stripe__title {
  margin: 0 0 var(--space-sm);
  font-family: var(--font-serif);
  font-size: var(--text-lg);
}

.advantage-stripe__text {
  margin: 0;
  font-size: var(--text-base);
  line-height: 1.7;
  max-width: 42em;
}

/* 页脚 */
.site-footer {
  padding: var(--space-md);
  text-align: center;
  font-size: var(--text-sm);
  background: var(--color-slate);
  color: var(--color-on-dark);
}

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

.site-footer a {
  color: var(--color-amber);
}

/* 手机横屏矮屏 */
@media (orientation: landscape) and (max-height: 500px) {
  .hero {
    padding-top: var(--space-md);
    padding-bottom: var(--space-md);
  }

  .hero__claim {
    font-size: clamp(1.25rem, 4vw, 1.5rem);
  }

  .hero__figure {
    width: min(100%, 7rem);
  }

  .top-bar {
    position: relative;
  }
}

/* 偏高竖屏 */
@media (max-aspect-ratio: 3/4) {
  .hero__inner {
    gap: var(--space-md);
  }

  .service-page {
    padding-top: var(--space-lg);
    padding-bottom: var(--space-lg);
  }
}

/* 平板 */
@media (min-width: 768px) {
  .top-bar__nav[hidden] {
    display: none;
  }

  .top-bar__nav:not([hidden]) {
    display: block;
  }

  .about__band {
    flex-direction: row;
    align-items: stretch;
    gap: var(--space-sm);
  }

  .about__labels {
    flex-direction: column;
    justify-content: space-between;
    flex: 0 0 auto;
    max-width: 8.5rem;
  }

  .about__body {
    flex: 1;
    min-width: 0;
  }

  .service-page {
    flex-direction: row;
    align-items: center;
    gap: var(--space-xl);
    padding-left: var(--space-lg);
    padding-right: var(--space-lg);
  }

  .service-page__text,
  .service-page__viz {
    flex: 1;
    min-width: 0;
  }

  .hero__inner {
    flex-direction: row;
    align-items: center;
  }

  .hero__copy {
    flex: 1.1;
    min-width: 0;
  }

  .hero__figure {
    flex: 0 0 min(38%, 14rem);
    align-self: stretch;
    display: flex;
    align-items: center;
  }
}

/* 桌面：左侧导航轨 */
@media (min-width: 1100px) {
  .top-bar {
    display: none;
  }

  .nav-rail {
    display: flex;
    flex-direction: column;
    align-items: center;
    position: fixed;
    left: 0;
    top: 0;
    bottom: 0;
    width: var(--nav-rail-width);
    z-index: 40;
    background: var(--color-slate);
    color: var(--color-on-dark);
    padding: var(--space-md) 0;
  }

  .nav-rail__brand {
    writing-mode: vertical-rl;
    margin: 0 0 var(--space-lg);
    font-family: var(--font-serif);
    letter-spacing: 0.2em;
    font-size: var(--text-sm);
    color: var(--color-amber);
  }

  .nav-rail__list {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
    flex: 1;
  }

  .nav-rail__link {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.35rem;
    font-size: 0.6875rem;
    color: rgba(240, 236, 230, 0.65);
    text-decoration: none;
    padding: 0.25rem;
    min-width: 2.75rem;
  }

  .nav-rail__dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: rgba(240, 236, 230, 0.35);
    transition: background 0.2s, transform 0.2s;
  }

  .nav-rail__link.is-active,
  .nav-rail__link:focus-visible {
    color: var(--color-on-dark);
  }

  .nav-rail__link.is-active .nav-rail__dot,
  .nav-rail__link:focus-visible .nav-rail__dot {
    background: var(--color-amber);
    transform: scale(1.25);
  }

  .floor-indicator {
    position: relative;
    width: 4px;
    flex: 1;
    max-height: 8rem;
    margin-top: var(--space-md);
    background: rgba(240, 236, 230, 0.15);
    border-radius: 2px;
  }

  .floor-indicator__thumb {
    position: absolute;
    left: 0;
    width: 100%;
    height: 25%;
    background: var(--color-amber);
    border-radius: 2px;
    transition: top 0.25s ease-out;
    top: 0;
  }

  body {
    padding-left: var(--nav-rail-width);
  }

  .canvas {
    max-width: calc(var(--max-canvas) + var(--space-xl));
    margin: 0 auto;
  }

  .hero {
    min-height: min(85vh, 40rem);
    display: flex;
    align-items: center;
  }

  .hero__inner {
    width: 100%;
  }
}

/* 宽屏 */
@media (min-width: 1440px) {
  :root {
    --max-canvas: 68rem;
  }

  .canvas {
    padding-left: var(--space-lg);
    padding-right: var(--space-lg);
  }

  .hero__copy {
    padding-right: var(--space-xl);
  }
}

/* 超宽 */
@media (min-aspect-ratio: 2/1) and (min-width: 1100px) {
  .hero__inner {
    max-width: 56rem;
  }

  .advantage-stripe__inner {
    display: grid;
    grid-template-columns: minmax(12rem, 22%) 1fr;
    gap: var(--space-lg);
    align-items: start;
  }

  .advantage-stripe__title {
    margin-bottom: 0;
  }
}

/* 手机横屏矮屏：放在全部宽度规则之后，压过 768px+ 首屏横排 */
@media (orientation: landscape) and (max-height: 500px) {
  :root {
    --top-bar-height: 2.5rem;
  }

  .top-bar {
    position: relative;
    min-height: var(--top-bar-height);
    padding: 0.2rem var(--space-sm);
  }

  .top-bar__title {
    font-size: 0.75rem;
  }

  .top-bar__toggle {
    min-height: 2rem;
    padding: 0.25rem 0.5rem;
    font-size: 0.75rem;
  }

  .hero {
    min-height: 0;
    display: block;
    padding: 0.35rem var(--space-sm) 0.5rem;
  }

  .hero__inner {
    flex-direction: row;
    align-items: center;
    gap: 0.5rem;
    max-width: 100%;
    max-height: calc(100svh - var(--top-bar-height));
  }

  .hero__copy {
    flex: 1 1 58%;
    min-width: 0;
  }

  .hero__claim {
    font-size: clamp(0.95rem, 2.6vw, 1.15rem);
    line-height: 1.25;
    margin-bottom: 0.2rem;
  }

  .hero__hook {
    font-size: clamp(0.75rem, 2vw, 0.875rem);
    margin-bottom: 0.2rem;
    line-height: 1.3;
  }

  .hero__sub {
    font-size: clamp(0.625rem, 1.6vw, 0.75rem);
    line-height: 1.35;
    margin-bottom: 0.35rem;
    max-width: none;
  }

  .hero__actions {
    gap: 0.35rem;
  }

  .btn {
    min-height: 2.25rem;
    padding: 0.25rem 0.55rem;
    font-size: 0.6875rem;
  }

  .hero__figure {
    flex: 0 0 auto;
    width: min(32%, 9rem);
    height: calc(100svh - var(--top-bar-height) - 0.8rem);
    max-height: calc(100svh - var(--top-bar-height) - 0.8rem);
    overflow: hidden;
    align-self: center;
    display: flex;
    align-items: center;
    justify-content: center;
  }

  .hero__topology {
    width: 100%;
    height: 100%;
    max-width: none;
    max-height: none;
  }
}