/* ==========================================================================
   Karser Official Website — Core Stylesheet
   Design Language: Minimalist Technology / Developer First / Premium SaaS
   Palette: Monochrome Gray & White (#FFFFFF / #F7F7F8 / #111113 / #68686F)
   ========================================================================== */

:root {
  /* Color Palette */
  --bg-primary: #FFFFFF;
  --bg-secondary: #F7F7F8;
  --bg-card: #FFFFFF;
  --bg-subtle-hover: #FAFAFB;
  --bg-dark: #111113;
  --bg-dark-surface: #18181B;
  --bg-dark-elevated: #1F1F23;

  --text-primary: #111113;
  --text-secondary: #68686F;
  --text-muted: #92929A;
  --text-on-dark: #F4F4F6;
  --text-on-dark-secondary: #A1A1AA;
  --text-on-dark-muted: #71717A;

  --border-default: #E8E8EB;
  --border-subtle: #F0F0F3;
  --border-strong: #D4D4D8;
  --border-focus: #111113;
  --border-dark: #27272A;
  --border-dark-hover: #52525B;

  /* Typography */
  --font-sans: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans CJK SC",
    "Source Han Sans SC", sans-serif;
  --font-mono: "JetBrains Mono", "SFMono-Regular", Menlo, Monaco, Consolas,
    "Liberation Mono", "Courier New", monospace;

  /* Fluid Type Scale */
  --text-xs: 0.75rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: clamp(1.0625rem, 1.2vw, 1.1875rem);
  --text-xl: clamp(1.1875rem, 1.5vw, 1.375rem);
  --text-h1: clamp(2rem, 4.2vw, 3.375rem);
  --text-h2: clamp(1.625rem, 3vw, 2.375rem);
  --text-h3: clamp(1.125rem, 1.6vw, 1.3125rem);

  /* Layout & Spacing */
  --container-max: 1200px;
  --container-pad: clamp(1.25rem, 4vw, 2.5rem);
  --header-height: 64px;
  --section-py: clamp(4.5rem, 8vw, 7.5rem);

  /* Radii & Shadows */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --shadow-subtle: 0 1px 2px rgba(17, 17, 19, 0.03);
  --shadow-card-hover: 0 12px 32px -8px rgba(17, 17, 19, 0.07),
    0 2px 6px -1px rgba(17, 17, 19, 0.04);

  /* Motion */
  --ease-out-expo: cubic-bezier(0.16, 1, 0.3, 1);
  --duration-fast: 180ms;
  --duration-base: 280ms;
  --duration-reveal: 560ms;
}

/* ==========================================================================
   1. Reset & Base Typography
   ========================================================================== */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
  scroll-padding-top: var(--header-height);
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: var(--text-base);
  line-height: 1.68;
  color: var(--text-primary);
  background-color: var(--bg-primary);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: clip;
  overflow-wrap: break-word;
  word-break: break-word;
}

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

img {
  height: auto;
  object-fit: contain;
}

a {
  color: inherit;
  text-decoration: none;
  transition: color var(--duration-fast) var(--ease-out-expo);
}

ul,
ol {
  list-style: none;
}

button {
  font: inherit;
  color: inherit;
  background: none;
  border: none;
  cursor: pointer;
}

/* Focus Accessibility */
:focus-visible {
  outline: 2px solid var(--border-focus);
  outline-offset: 3px;
}

.infra-dark-section :focus-visible {
  outline-color: var(--text-on-dark);
}

.skip-link {
  position: absolute;
  top: -100px;
  left: 1rem;
  z-index: 9999;
  padding: 0.625rem 1rem;
  background: var(--text-primary);
  color: var(--bg-primary);
  font-size: var(--text-sm);
  font-weight: 500;
  border-radius: var(--radius-sm);
  transition: top var(--duration-fast) ease;
}

.skip-link:focus {
  top: 0.75rem;
}

/* Container */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--container-pad);
}

.section {
  position: relative;
  padding-block: var(--section-py);
  border-top: 1px solid var(--border-default);
}

/* Section Headers */
.section-header {
  max-width: 720px;
  margin-bottom: clamp(2.5rem, 5vw, 4rem);
}

.section-eyebrow {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-secondary);
  margin-bottom: 0.75rem;
}

.section-title {
  font-size: var(--text-h2);
  font-weight: 700;
  line-height: 1.18;
  letter-spacing: -0.025em;
  color: var(--text-primary);
  margin-bottom: 1rem;
}

.section-subtitle {
  font-size: var(--text-lg);
  line-height: 1.65;
  color: var(--text-secondary);
}

/* ==========================================================================
   2. Buttons
   ========================================================================== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  min-height: 44px;
  padding: 0.6875rem 1.375rem;
  font-size: 0.9375rem;
  font-weight: 500;
  line-height: 1.2;
  border-radius: var(--radius-sm);
  border: 1px solid transparent;
  transition:
    background-color var(--duration-fast) var(--ease-out-expo),
    color var(--duration-fast) var(--ease-out-expo),
    border-color var(--duration-fast) var(--ease-out-expo),
    transform var(--duration-fast) var(--ease-out-expo),
    box-shadow var(--duration-fast) var(--ease-out-expo);
  user-select: none;
  white-space: nowrap;
}

.btn-primary {
  background-color: var(--text-primary);
  color: var(--bg-primary);
  border-color: var(--text-primary);
}

.btn-primary:hover {
  background-color: #27272A;
  border-color: #27272A;
  box-shadow: 0 4px 14px rgba(17, 17, 19, 0.14);
}

.btn-primary:active {
  transform: translateY(1px) scale(0.99);
}

.btn-secondary {
  background-color: var(--bg-primary);
  color: var(--text-primary);
  border-color: var(--border-strong);
}

.btn-secondary:hover {
  background-color: var(--bg-secondary);
  border-color: var(--text-primary);
}

.btn-secondary:active {
  transform: translateY(1px) scale(0.99);
}

.btn-icon-arrow {
  transition: transform var(--duration-base) var(--ease-out-expo);
}

.btn:hover .btn-icon-arrow {
  transform: translateX(3px);
}

/* ==========================================================================
   3. Top Navigation Bar
   ========================================================================== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  width: 100%;
  height: var(--header-height);
  background-color: rgba(255, 255, 255, 0.82);
  backdrop-filter: saturate(180%) blur(10px);
  -webkit-backdrop-filter: saturate(180%) blur(10px);
  border-bottom: 1px solid rgba(232, 232, 235, 0.65);
  transition:
    background-color var(--duration-base) var(--ease-out-expo),
    border-color var(--duration-base) var(--ease-out-expo),
    box-shadow var(--duration-base) var(--ease-out-expo);
}

.site-header.is-scrolled {
  background-color: rgba(255, 255, 255, 0.96);
  border-bottom-color: var(--border-default);
  box-shadow: 0 1px 3px rgba(17, 17, 19, 0.03);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
  gap: 1.5rem;
}

.brand-link {
  display: inline-flex;
  align-items: center;
  gap: 0.625rem;
  font-weight: 600;
  color: var(--text-primary);
  flex-shrink: 0;
}

.brand-logo {
  width: 28px;
  height: 28px;
  border-radius: 6px;
  object-fit: contain;
}

.brand-mark-fallback {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  border-radius: 6px;
  background: var(--text-primary);
  color: var(--bg-primary);
  font-family: var(--font-mono);
  font-size: 0.875rem;
  font-weight: 700;
}

.brand-name {
  font-size: 1.0625rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.brand-divider {
  color: var(--border-strong);
  font-weight: 300;
}

.brand-sub {
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  font-weight: 500;
  letter-spacing: 0.08em;
  color: var(--text-muted);
}

/* Primary Nav */
.primary-nav {
  display: flex;
  align-items: center;
}

.nav-list {
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

.nav-link {
  position: relative;
  display: inline-flex;
  align-items: baseline;
  gap: 0.35rem;
  padding: 0.4375rem 0.75rem;
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  transition:
    color var(--duration-fast) var(--ease-out-expo),
    background-color var(--duration-fast) var(--ease-out-expo);
}

.nav-label-en {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-muted);
  transition: color var(--duration-fast) var(--ease-out-expo);
}

.nav-link:hover,
.nav-link.is-active {
  color: var(--text-primary);
  background-color: var(--bg-secondary);
}

.nav-link:hover .nav-label-en,
.nav-link.is-active .nav-label-en {
  color: var(--text-secondary);
}

/* Mobile Menu Button */
.mobile-menu-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: 5px;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-default);
  background-color: var(--bg-primary);
  transition: border-color var(--duration-fast) ease;
}

.mobile-menu-toggle:hover {
  border-color: var(--text-primary);
}

.toggle-bar {
  display: block;
  width: 16px;
  height: 1.5px;
  background-color: var(--text-primary);
  transition: transform var(--duration-base) var(--ease-out-expo);
}

.mobile-menu-toggle[aria-expanded="true"] .toggle-bar:first-child {
  transform: translateY(3.25px) rotate(45deg);
}

.mobile-menu-toggle[aria-expanded="true"] .toggle-bar:last-child {
  transform: translateY(-3.25px) rotate(-45deg);
}

/* Mobile Drawer */
.mobile-nav-drawer {
  position: absolute;
  top: var(--header-height);
  left: 0;
  right: 0;
  background-color: var(--bg-primary);
  border-bottom: 1px solid var(--border-default);
  box-shadow: 0 12px 24px rgba(17, 17, 19, 0.06);
}

.mobile-nav-drawer[hidden] {
  display: none;
}

.mobile-nav-inner {
  padding-block: 1rem;
}

.mobile-nav-list {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.mobile-nav-link {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.75rem 0.875rem;
  border-radius: var(--radius-sm);
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--text-primary);
  transition: background-color var(--duration-fast) ease;
}

.mobile-nav-link:hover {
  background-color: var(--bg-secondary);
}

.mobile-nav-en {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--text-muted);
}

/* ==========================================================================
   4. Hero Section (#home)
   ========================================================================== */
.hero-section {
  position: relative;
  padding-top: clamp(3.5rem, 7vw, 6.25rem);
  padding-bottom: clamp(3.5rem, 6vw, 5.5rem);
  overflow: hidden;
  background-color: var(--bg-primary);
}

.hero-grid-backdrop {
  position: absolute;
  inset: 0;
  pointer-events: none;
  background-image:
    linear-gradient(to right, rgba(232, 232, 235, 0.55) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(232, 232, 235, 0.55) 1px, transparent 1px);
  background-size: 64px 64px;
  mask-image: radial-gradient(ellipse 80% 70% at 50% 35%, #000 35%, transparent 100%);
  -webkit-mask-image: radial-gradient(ellipse 80% 70% at 50% 35%, #000 35%, transparent 100%);
  will-change: transform;
}

.grid-crosshair {
  position: absolute;
  width: 11px;
  height: 11px;
}

.grid-crosshair::before,
.grid-crosshair::after {
  content: "";
  position: absolute;
  background-color: var(--text-muted);
}

.grid-crosshair::before {
  top: 5px;
  left: 0;
  width: 11px;
  height: 1px;
}

.grid-crosshair::after {
  top: 0;
  left: 5px;
  width: 1px;
  height: 11px;
}

.crosshair-tl { top: 64px; left: 12%; }
.crosshair-tr { top: 64px; right: 12%; }
.crosshair-bl { bottom: 128px; left: 12%; }
.crosshair-br { bottom: 128px; right: 12%; }

.hero-container {
  position: relative;
  z-index: 1;
}

.hero-layout {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: clamp(2rem, 4.5vw, 4rem);
  align-items: center;
}

.hero-copy {
  max-width: 640px;
}

.hero-eyebrow-wrap {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.3125rem 0.75rem;
  margin-bottom: 1.5rem;
  border: 1px solid var(--border-default);
  border-radius: 999px;
  background-color: var(--bg-secondary);
}

.hero-eyebrow-dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background-color: var(--text-primary);
}

.hero-eyebrow-text {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.06em;
  color: var(--text-secondary);
}

.hero-title {
  font-size: var(--text-h1);
  font-weight: 700;
  line-height: 1.12;
  letter-spacing: -0.032em;
  color: var(--text-primary);
  margin-bottom: 1.375rem;
}

.hero-title-line {
  display: block;
}

.hero-title-accent {
  color: #3F3F46;
}

.hero-subtitle-zh {
  font-size: var(--text-xl);
  font-weight: 600;
  line-height: 1.5;
  color: var(--text-primary);
  margin-bottom: 0.875rem;
}

.hero-description {
  font-size: var(--text-base);
  line-height: 1.75;
  color: var(--text-secondary);
  margin-bottom: 2.25rem;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.875rem;
}

/* Right Column Blueprint Visual */
.hero-visual-wrap {
  width: 100%;
  will-change: transform;
}

.infra-blueprint-card {
  background-color: var(--bg-card);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-subtle);
  overflow: hidden;
}

.blueprint-top-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  padding: 0.75rem 1rem;
  background-color: var(--bg-secondary);
  border-bottom: 1px solid var(--border-default);
  font-family: var(--font-mono);
  font-size: 0.6875rem;
}

.blueprint-code {
  color: var(--text-primary);
  font-weight: 600;
}

.blueprint-tag {
  color: var(--text-muted);
}

.blueprint-svg {
  width: 100%;
  height: auto;
  padding: 0.75rem;
  background-color: var(--bg-primary);
}

.blueprint-footer {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 0.5rem;
  padding: 0.75rem 1rem;
  background-color: var(--bg-secondary);
  border-top: 1px solid var(--border-default);
}

.blueprint-pill {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-family: var(--font-mono);
  font-size: 0.6875rem;
}

.pill-key {
  color: var(--text-muted);
}

.pill-val {
  color: var(--text-primary);
  font-weight: 600;
}

/* Hero Bottom Domain Strip */
.hero-domain-strip {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  margin-top: clamp(3rem, 6vw, 4.75rem);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  background-color: var(--bg-secondary);
  overflow: hidden;
}

.domain-strip-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 1rem 1.25rem;
  border-right: 1px solid var(--border-default);
}

.domain-strip-item:last-child {
  border-right: none;
}

.domain-index {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 600;
  color: var(--text-muted);
}

.domain-name-zh {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-primary);
}

/* ==========================================================================
   5. Technology Capabilities Section (#technology)
   ========================================================================== */
.tech-section {
  background-color: var(--bg-secondary);
}

.tech-cards-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
  align-items: stretch;
}

.tech-card {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  background-color: var(--bg-card);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  padding: 2rem;
  transition:
    border-color var(--duration-base) var(--ease-out-expo),
    box-shadow var(--duration-base) var(--ease-out-expo),
    background-color var(--duration-base) var(--ease-out-expo);
}

.tech-card:hover {
  border-color: var(--text-primary);
  box-shadow: var(--shadow-card-hover);
  background-color: var(--bg-subtle-hover);
}

.tech-card-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1.75rem;
}

.tech-icon-box {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-default);
  background-color: var(--bg-secondary);
  color: var(--text-primary);
  transition:
    transform var(--duration-base) var(--ease-out-expo),
    background-color var(--duration-base) var(--ease-out-expo),
    color var(--duration-base) var(--ease-out-expo),
    border-color var(--duration-base) var(--ease-out-expo);
}

.tech-card:hover .tech-icon-box {
  transform: translateY(-2px);
  background-color: var(--text-primary);
  color: var(--bg-primary);
  border-color: var(--text-primary);
}

.tech-card-index {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 600;
  color: var(--text-muted);
}

.tech-card-body {
  flex: 1;
}

.tech-card-title-en {
  font-size: var(--text-h3);
  font-weight: 700;
  line-height: 1.3;
  letter-spacing: -0.015em;
  color: var(--text-primary);
  margin-bottom: 0.375rem;
}

.tech-card-title-zh {
  font-size: 0.9375rem;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 1rem;
}

.tech-card-desc {
  font-size: 0.9375rem;
  line-height: 1.7;
  color: var(--text-secondary);
  margin-bottom: 1.5rem;
}

.tech-cap-list {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  padding-top: 1.25rem;
  border-top: 1px solid var(--border-subtle);
  margin-bottom: 1.75rem;
}

.tech-cap-item {
  display: flex;
  align-items: baseline;
  gap: 0.625rem;
  font-size: 0.875rem;
  color: var(--text-primary);
}

.cap-bullet {
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background-color: var(--text-muted);
  flex-shrink: 0;
  transform: translateY(-2px);
}

.tech-card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border-default);
}

.tech-card-tag {
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  font-weight: 500;
  letter-spacing: 0.04em;
  color: var(--text-muted);
}

.tech-card-arrow {
  display: inline-flex;
  color: var(--text-secondary);
  transition:
    transform var(--duration-base) var(--ease-out-expo),
    color var(--duration-base) var(--ease-out-expo);
}

.tech-card:hover .tech-card-arrow {
  transform: translate(2px, -2px);
  color: var(--text-primary);
}

/* ==========================================================================
   6. About Karser Section (#about)
   ========================================================================== */
.about-section {
  background-color: var(--bg-primary);
}

.about-layout {
  display: grid;
  grid-template-columns: 1fr 1.1fr;
  gap: clamp(2.5rem, 5vw, 4.5rem);
  align-items: start;
}

.about-title {
  margin-bottom: 1.25rem;
}

.about-company-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.375rem 0.875rem;
  margin-bottom: 1.5rem;
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-primary);
}

.company-badge-dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background-color: var(--text-primary);
}

.about-lead {
  font-size: var(--text-lg);
  font-weight: 500;
  line-height: 1.68;
  color: var(--text-primary);
  margin-bottom: 1.25rem;
}

.about-paragraph {
  font-size: 0.9375rem;
  line-height: 1.8;
  color: var(--text-secondary);
  margin-bottom: 1rem;
}

.about-paragraph:last-child {
  margin-bottom: 0;
}

/* Right Column: 2x2 Engineering Pillars */
.about-pillars-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1px;
  background-color: var(--border-default);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.pillar-card {
  background-color: var(--bg-card);
  padding: 1.75rem;
  transition: background-color var(--duration-base) var(--ease-out-expo);
}

.pillar-card:hover {
  background-color: var(--bg-secondary);
}

.pillar-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  margin-bottom: 1rem;
}

.pillar-code {
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  font-weight: 600;
  color: var(--text-primary);
  padding: 0.1875rem 0.5rem;
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-default);
  border-radius: 4px;
}

.pillar-en {
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  color: var(--text-muted);
}

.pillar-title {
  font-size: 1.0625rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 0.625rem;
}

.pillar-detail {
  font-size: 0.875rem;
  line-height: 1.7;
  color: var(--text-secondary);
}

/* ==========================================================================
   7. Dark Developer Infrastructure Block (#cloud)
   ========================================================================== */
.infra-dark-section {
  position: relative;
  background-color: var(--bg-dark);
  color: var(--text-on-dark);
  border-top-color: var(--border-dark);
  overflow: hidden;
}

.infra-grid-overlay {
  position: absolute;
  inset: 0;
  pointer-events: none;
  background-image:
    linear-gradient(to right, rgba(255, 255, 255, 0.04) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(255, 255, 255, 0.04) 1px, transparent 1px);
  background-size: 56px 56px;
  will-change: transform;
}

.infra-container {
  position: relative;
  z-index: 1;
}

.infra-eyebrow {
  color: var(--text-on-dark-muted);
}

.infra-title {
  color: var(--text-on-dark);
}

.infra-subtitle {
  color: var(--text-on-dark-secondary);
}

.infra-showcase-grid {
  display: grid;
  grid-template-columns: 1.05fr 0.95fr;
  gap: 2rem;
  align-items: stretch;
}

.infra-layers-col {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.infra-layer-card {
  background-color: var(--bg-dark-surface);
  border: 1px solid var(--border-dark);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  cursor: pointer;
  transition:
    border-color var(--duration-base) var(--ease-out-expo),
    background-color var(--duration-base) var(--ease-out-expo);
}

.infra-layer-card:hover,
.infra-layer-card.is-active {
  border-color: var(--text-on-dark-secondary);
  background-color: var(--bg-dark-elevated);
}

.layer-card-top {
  display: flex;
  align-items: flex-start;
  gap: 0.875rem;
  margin-bottom: 0.75rem;
}

.layer-badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 36px;
  height: 28px;
  padding-inline: 0.5rem;
  border-radius: 4px;
  background-color: var(--bg-dark);
  border: 1px solid var(--border-dark-hover);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-on-dark);
}

.infra-layer-card.is-active .layer-badge {
  background-color: var(--text-on-dark);
  color: var(--bg-dark);
  border-color: var(--text-on-dark);
}

.layer-name-en {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-on-dark);
  line-height: 1.3;
}

.layer-name-zh {
  font-size: 0.8125rem;
  color: var(--text-on-dark-secondary);
  margin-top: 0.15rem;
}

.layer-summary {
  font-size: 0.875rem;
  line-height: 1.68;
  color: var(--text-on-dark-secondary);
  margin-bottom: 1rem;
}

.layer-modules {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.layer-module-chip {
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  color: var(--text-on-dark);
  background-color: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--border-dark);
  padding: 0.25rem 0.625rem;
  border-radius: 4px;
}

/* Right Schematic Window */
.schematic-window {
  display: flex;
  flex-direction: column;
  height: 100%;
  background-color: #141417;
  border: 1px solid var(--border-dark);
  border-radius: var(--radius-md);
  overflow: hidden;
}

.schematic-window-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  padding: 0.75rem 1rem;
  background-color: var(--bg-dark-surface);
  border-bottom: 1px solid var(--border-dark);
  font-family: var(--font-mono);
  font-size: 0.6875rem;
}

.window-dots {
  display: flex;
  gap: 6px;
}

.window-dots span {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background-color: #3F3F46;
}

.window-filename {
  color: var(--text-on-dark);
}

.window-mode {
  color: var(--text-on-dark-muted);
}

.schematic-window-body {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  flex: 1;
  padding: 1.5rem;
  gap: 1.5rem;
}

.schematic-diagram {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.diagram-row {
  display: flex;
  align-items: center;
  gap: 0.875rem;
  padding: 0.875rem 1rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-dark);
  background-color: var(--bg-dark-surface);
  transition:
    border-color var(--duration-base) ease,
    background-color var(--duration-base) ease;
}

.diagram-row.is-highlighted {
  border-color: var(--text-on-dark);
  background-color: var(--bg-dark-elevated);
}

.diagram-node-id {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--text-on-dark-muted);
}

.diagram-row.is-highlighted .diagram-node-id {
  color: var(--text-on-dark);
}

.diagram-node-box {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  width: 100%;
  gap: 0.5rem;
}

.node-title {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-on-dark);
}

.node-meta {
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  color: var(--text-on-dark-muted);
}

.diagram-connector {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding-left: 1.5rem;
}

.connector-line {
  width: 1px;
  height: 18px;
  background-color: #3F3F46;
}

.connector-label {
  font-family: var(--font-mono);
  font-size: 0.625rem;
  letter-spacing: 0.06em;
  color: var(--text-on-dark-muted);
}

.schematic-code {
  padding: 1rem;
  border-radius: var(--radius-sm);
  background-color: var(--bg-dark);
  border: 1px solid var(--border-dark);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  line-height: 1.65;
  color: var(--text-on-dark-secondary);
  overflow-x: auto;
}

.code-comment { color: #71717A; }
.code-key { color: #E4E4E7; }
.code-str { color: #A1A1AA; }
.code-val { color: #FAFAFA; font-weight: 600; }

/* ==========================================================================
   8. Contact Section (#contact)
   ========================================================================== */
.contact-section {
  background-color: var(--bg-primary);
}

.contact-card {
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  background-color: var(--bg-secondary);
  padding: clamp(2rem, 4.5vw, 3.5rem);
}

.contact-grid {
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: clamp(2rem, 4vw, 3.5rem);
  align-items: center;
}

.contact-title {
  margin-bottom: 1rem;
}

.contact-desc {
  font-size: var(--text-lg);
  line-height: 1.68;
  color: var(--text-secondary);
  margin-bottom: 1.75rem;
}

.contact-notice-box {
  background-color: var(--bg-card);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  padding: 1.5rem;
}

.contact-notice-text {
  font-size: 0.9375rem;
  line-height: 1.75;
  color: var(--text-secondary);
  margin-bottom: 1.25rem;
}

.contact-entity-tag {
  display: inline-flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.625rem;
  padding-top: 0.875rem;
  border-top: 1px solid var(--border-subtle);
  font-size: 0.875rem;
}

.entity-label {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-muted);
}

.entity-name {
  font-weight: 600;
  color: var(--text-primary);
}

.contact-channels {
  display: flex;
  flex-direction: column;
  gap: 0.875rem;
  margin-bottom: 1.75rem;
}

.contact-channel-item {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 0.75rem;
  padding: 0.875rem 1rem;
  background-color: var(--bg-card);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-sm);
}

.channel-label {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-muted);
  min-width: 130px;
}

.channel-value {
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--text-primary);
}

.channel-link:hover {
  text-decoration: underline;
}

/* Contact Aside Focus Panel */
.contact-focus-panel {
  background-color: var(--bg-card);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  padding: 1.75rem;
}

.focus-panel-title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 0.25rem;
}

.focus-panel-sub {
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  margin-bottom: 1.25rem;
}

.focus-area-list {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.focus-area-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.625rem 0.75rem;
  border-radius: var(--radius-sm);
  background-color: var(--bg-secondary);
  font-size: 0.875rem;
  color: var(--text-primary);
}

.focus-area-num {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-muted);
}

/* ==========================================================================
   9. Site Footer & Filing Info
   ========================================================================== */
.site-footer {
  background-color: var(--bg-secondary);
  border-top: 1px solid var(--border-default);
  padding-top: clamp(3rem, 5vw, 4.5rem);
  padding-bottom: clamp(2.25rem, 4vw, 3rem);
  color: var(--text-secondary);
}

.footer-top-grid {
  display: grid;
  grid-template-columns: 1.5fr 1fr 1.2fr;
  gap: 2.5rem;
  padding-bottom: 2.75rem;
  border-bottom: 1px solid var(--border-default);
}

.footer-brand-header {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.75rem;
}

.footer-logo {
  width: 24px;
  height: 24px;
  border-radius: 5px;
}

.footer-brand-name {
  font-size: 1.0625rem;
  font-weight: 700;
  color: var(--text-primary);
}

.footer-company-title {
  font-size: 0.9375rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 0.5rem;
}

.footer-tagline {
  font-size: 0.875rem;
  line-height: 1.65;
  color: var(--text-secondary);
  max-width: 360px;
}

.footer-col-heading {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--text-primary);
  margin-bottom: 1rem;
}

.footer-nav-list,
.footer-domain-list {
  display: flex;
  flex-direction: column;
  gap: 0.625rem;
  font-size: 0.875rem;
}

.footer-link {
  color: var(--text-secondary);
}

.footer-link:hover {
  color: var(--text-primary);
}

.footer-link-en {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-left: 0.25rem;
}

.footer-bottom {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 1rem 2rem;
  padding-top: 1.75rem;
  font-size: 0.875rem;
}

.footer-filing-group,
.footer-copyright-group {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.625rem 0.875rem;
}

.filing-item {
  display: inline-flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.4rem;
}

.police-filing-icon {
  width: 20px;
  height: 20px;
  flex-shrink: 0;
}

.filing-link {
  color: var(--text-secondary);
  font-weight: 500;
}

.filing-link:hover {
  color: var(--text-primary);
  text-decoration: underline;
}

.filing-status-badge {
  display: inline-flex;
  align-items: center;
  padding: 0.1rem 0.45rem;
  font-size: 0.75rem;
  color: var(--text-secondary);
  background-color: var(--bg-primary);
  border: 1px solid var(--border-default);
  border-radius: 4px;
}

.filing-sep {
  color: var(--border-strong);
}

.footer-company-legal {
  color: var(--text-primary);
  font-weight: 500;
}

.footer-copyright {
  color: var(--text-muted);
}

/* ==========================================================================
   10. Error Pages (404 / 500)
   ========================================================================== */
.error-section {
  padding-block: clamp(5rem, 12vw, 9rem);
}

.error-container {
  max-width: 640px;
}

.error-card {
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  background-color: var(--bg-secondary);
  padding: clamp(2rem, 5vw, 3.5rem);
  text-align: center;
}

.error-code {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  padding: 0.25rem 0.75rem;
  border-radius: 999px;
  background-color: var(--bg-primary);
  border: 1px solid var(--border-default);
  color: var(--text-secondary);
  margin-bottom: 1rem;
}

.error-title {
  font-size: var(--text-h2);
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 0.875rem;
}

.error-desc {
  font-size: 0.9375rem;
  color: var(--text-secondary);
  margin-bottom: 2rem;
}

/* ==========================================================================
   11. Motion & Entrance Animations (Progressive Enhancement)
   ========================================================================== */
@keyframes heroFadeUp {
  from {
    opacity: 0;
    transform: translateY(12px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

html.js-ready[data-animations="enabled"] .hero-entry {
  opacity: 0;
  animation: heroFadeUp 520ms var(--ease-out-expo) forwards;
}

html.js-ready[data-animations="enabled"] .hero-entry-1 { animation-delay: 40ms; }
html.js-ready[data-animations="enabled"] .hero-entry-2 { animation-delay: 100ms; }
html.js-ready[data-animations="enabled"] .hero-entry-3 { animation-delay: 160ms; }
html.js-ready[data-animations="enabled"] .hero-entry-4 { animation-delay: 220ms; }
html.js-ready[data-animations="enabled"] .hero-entry-5 { animation-delay: 280ms; }

html.js-ready[data-animations="enabled"] .reveal-item {
  opacity: 0;
  transform: translateY(16px);
  transition:
    opacity var(--duration-reveal) var(--ease-out-expo),
    transform var(--duration-reveal) var(--ease-out-expo);
  transition-delay: calc(var(--stagger-index, 0) * 70ms);
}

html.js-ready[data-animations="enabled"] .reveal-item.is-visible {
  opacity: 1;
  transform: translateY(0);
}

/* Reduced Motion Accessibility */
@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }

  html.js-ready[data-animations="enabled"] .hero-entry,
  html.js-ready[data-animations="enabled"] .reveal-item {
    opacity: 1 !important;
    transform: none !important;
  }
}

/* ==========================================================================
   12. Responsive Breakpoints (1440px, 1024px, 768px, 375px, 320px)
   ========================================================================== */

/* Tablet & Small Laptop (<= 1024px) */
@media (max-width: 1024px) {
  .hero-layout {
    grid-template-columns: 1fr;
    gap: 2.5rem;
  }

  .hero-copy {
    max-width: 100%;
  }

  .hero-domain-strip {
    grid-template-columns: repeat(2, 1fr);
  }

  .domain-strip-item:nth-child(2) {
    border-right: none;
  }

  .domain-strip-item:nth-child(1),
  .domain-strip-item:nth-child(2) {
    border-bottom: 1px solid var(--border-default);
  }

  .tech-cards-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .about-layout {
    grid-template-columns: 1fr;
  }

  .infra-showcase-grid {
    grid-template-columns: 1fr;
  }

  .contact-grid {
    grid-template-columns: 1fr;
  }

  .footer-top-grid {
    grid-template-columns: 1fr 1fr;
  }
}

/* Mobile & Narrow Tablet (<= 768px) */
@media (max-width: 768px) {
  .primary-nav {
    display: none;
  }

  .mobile-menu-toggle {
    display: inline-flex;
  }

  .brand-divider,
  .brand-sub {
    display: none;
  }

  .hero-domain-strip {
    grid-template-columns: 1fr;
  }

  .domain-strip-item {
    border-right: none !important;
    border-bottom: 1px solid var(--border-default);
  }

  .domain-strip-item:last-child {
    border-bottom: none;
  }

  .tech-cards-grid {
    grid-template-columns: 1fr;
  }

  .about-pillars-grid {
    grid-template-columns: 1fr;
  }

  .footer-top-grid {
    grid-template-columns: 1fr;
    gap: 2rem;
  }

  .footer-bottom {
    flex-direction: column;
    align-items: flex-start;
  }

  .filing-sep {
    display: none;
  }

  .footer-filing-group,
  .footer-copyright-group {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.5rem;
  }
}

/* Compact Mobile (<= 375px & 320px) */
@media (max-width: 400px) {
  :root {
    --container-pad: 1rem;
  }

  .hero-actions {
    flex-direction: column;
    align-items: stretch;
  }

  .hero-actions .btn {
    width: 100%;
  }

  .tech-card,
  .pillar-card,
  .contact-card,
  .contact-focus-panel {
    padding: 1.25rem;
  }

  .schematic-window-body {
    padding: 1rem;
  }
}