/* ============================================================
   Chase Grand — Songyuan Zhuhong Network Technology Co., Ltd.
   Bold. Technical. Uncompromising.
   ============================================================ */

/* ----------------------------------------------------------
   0. Custom Properties
   ---------------------------------------------------------- */
:root {
  --cg-black: #080808;
  --cg-offblack: #111111;
  --cg-dark: #1a1a1a;
  --cg-gold: #f0c040;
  --cg-gold-bright: #f5d060;
  --cg-gold-deep: #c49820;
  --cg-white: #f5f5f5;
  --cg-offwhite: #e0e0e0;
  --cg-gray: #999999;
  --cg-midgray: #666666;
  --cg-darkgray: #333333;
  --cg-red: #e04040;

  --font-body: 'DM Sans', system-ui, -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', 'SF Mono', 'Cascadia Code', monospace;

  --base: 1.0625rem;           /* 17px */
  --leading: 1.6;
  --measure: 68ch;

  --space-xs: 0.5rem;
  --space-sm: 1rem;
  --space-md: 2rem;
  --space-lg: 4rem;
  --space-xl: 6rem;
  --space-2xl: 10rem;

  --header-h: 4.5rem;
  --border-thin: 1px solid var(--cg-darkgray);
  --ease-out: cubic-bezier(0.22, 0.61, 0.36, 1);
  --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);
}

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

html {
  font-size: var(--base);
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-body);
  font-weight: 300;
  line-height: var(--leading);
  color: var(--cg-offwhite);
  background: var(--cg-black);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

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

a {
  color: inherit;
  text-decoration: none;
}

ul, ol {
  list-style: none;
}

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

input, textarea, select {
  font: inherit;
  color: inherit;
}

::selection {
  background: var(--cg-gold);
  color: var(--cg-black);
}

::placeholder {
  color: var(--cg-midgray);
}

:focus-visible {
  outline: 2px solid var(--cg-gold);
  outline-offset: 2px;
}

/* ----------------------------------------------------------
   2. Skip Link
   ---------------------------------------------------------- */
.skip-link {
  position: absolute;
  top: -100%;
  left: var(--space-md);
  background: var(--cg-gold);
  color: var(--cg-black);
  padding: var(--space-xs) var(--space-sm);
  font-weight: 700;
  font-size: 0.9rem;
  z-index: 1000;
  border-radius: 0 0 4px 4px;
}

.skip-link:focus {
  top: 0;
}

/* ----------------------------------------------------------
   3. Header & Navigation
   ---------------------------------------------------------- */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: var(--header-h);
  background: var(--cg-black);
  border-bottom: var(--border-thin);
  z-index: 900;
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 var(--space-md);
  height: 100%;
}

/* Logo */
.logo {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  z-index: 10;
}

.logo-mark {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 2.4rem;
  height: 2.4rem;
  background: var(--cg-gold);
  color: var(--cg-black);
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 1rem;
  border-radius: 6px;
  letter-spacing: -0.02em;
  flex-shrink: 0;
}

.logo-text {
  font-size: 1.15rem;
  font-weight: 500;
  letter-spacing: -0.01em;
  color: var(--cg-white);
}

.logo-accent {
  color: var(--cg-gold);
  font-weight: 700;
}

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

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

.nav-link {
  display: block;
  padding: 0.5rem 1rem;
  font-size: 0.9rem;
  font-weight: 500;
  letter-spacing: 0.02em;
  color: var(--cg-gray);
  transition: color 0.2s ease;
  border-radius: 4px;
}

.nav-link:hover,
.nav-link:focus-visible {
  color: var(--cg-white);
}

/* Nav Toggle (mobile) */
.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  width: 2.2rem;
  height: 2.2rem;
  align-items: center;
  justify-content: center;
  z-index: 10;
  padding: 0.3rem;
}

.nav-toggle-bar {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--cg-white);
  border-radius: 1px;
  transition: transform 0.3s var(--ease-out), opacity 0.2s ease;
}

.nav-toggle[aria-expanded="true"] .nav-toggle-bar:first-child {
  transform: translateY(7px) rotate(45deg);
}

.nav-toggle[aria-expanded="true"] .nav-toggle-bar:last-child {
  transform: translateY(-7px) rotate(-45deg);
}

/* ----------------------------------------------------------
   4. Billboard / Hero
   ---------------------------------------------------------- */
.billboard {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: calc(var(--header-h) + var(--space-xl)) var(--space-md) var(--space-xl);
  position: relative;
  overflow: hidden;
}

.billboard::before {
  content: '';
  position: absolute;
  top: 0;
  right: 0;
  width: 50%;
  height: 100%;
  background:
    radial-gradient(ellipse at 70% 30%, var(--cg-darkgray) 0%, transparent 70%),
    radial-gradient(ellipse at 80% 60%, rgba(240, 192, 64, 0.06) 0%, transparent 50%);
  pointer-events: none;
  z-index: 0;
}

.billboard-grid {
  max-width: 1100px;
  margin: 0 auto;
  width: 100%;
  position: relative;
  z-index: 1;
}

.billboard-rule {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  margin-bottom: var(--space-lg);
}

.rule-label {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--cg-gold);
  white-space: nowrap;
}

.rule-line {
  flex: 1;
  height: 1px;
  background: var(--cg-darkgray);
}

.billboard-headline {
  font-size: clamp(2.8rem, 7vw, 5.5rem);
  font-weight: 700;
  line-height: 1.05;
  letter-spacing: -0.03em;
  color: var(--cg-white);
  max-width: 16ch;
  margin-bottom: var(--space-lg);
}

.headline-row {
  display: block;
}

.headline-emphasis {
  color: var(--cg-gold);
  position: relative;
}

.headline-emphasis::after {
  content: '';
  position: absolute;
  left: 0;
  bottom: 0.05em;
  width: 100%;
  height: 0.08em;
  background: var(--cg-gold);
  opacity: 0.4;
}

.billboard-statement {
  max-width: var(--measure);
}

.statement-large {
  font-size: 1.2rem;
  font-weight: 300;
  line-height: 1.7;
  color: var(--cg-offwhite);
  margin-bottom: var(--space-md);
}

.statement-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  align-items: center;
}

/* Buttons */
.btn-primary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.85rem 2rem;
  background: var(--cg-gold);
  color: var(--cg-black);
  font-weight: 700;
  font-size: 0.9rem;
  letter-spacing: 0.03em;
  border-radius: 4px;
  transition: background 0.2s ease, transform 0.15s var(--ease-out);
  text-align: center;
}

.btn-primary:hover {
  background: var(--cg-gold-bright);
  transform: translateY(-1px);
}

.btn-primary:active {
  transform: translateY(0);
}

.btn-ghost {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.85rem 1.5rem;
  color: var(--cg-white);
  font-weight: 500;
  font-size: 0.9rem;
  letter-spacing: 0.02em;
  border: 1px solid var(--cg-darkgray);
  border-radius: 4px;
  transition: border-color 0.2s ease, background 0.2s ease;
}

.btn-ghost:hover {
  border-color: var(--cg-gray);
  background: var(--cg-dark);
}

/* Marquee */
.billboard-marquee {
  display: flex;
  gap: 1.5rem;
  align-items: center;
  max-width: 1100px;
  margin: var(--space-xl) auto 0;
  width: 100%;
  overflow: hidden;
  position: relative;
  z-index: 1;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--cg-darkgray);
  white-space: nowrap;
}

.billboard-marquee span {
  flex-shrink: 0;
}

.marquee-dot {
  display: inline-block;
  width: 4px;
  height: 4px;
  border-radius: 50%;
  background: var(--cg-gold);
  opacity: 0.6;
  flex-shrink: 0;
}

/* ----------------------------------------------------------
   5. Section Shared
   ---------------------------------------------------------- */
section {
  padding: var(--space-2xl) var(--space-md);
  max-width: 1100px;
  margin: 0 auto;
}

.section-overline {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  margin-bottom: var(--space-sm);
}

.overline-num {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 500;
  color: var(--cg-gold);
  letter-spacing: 0.05em;
}

.overline-label {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--cg-midgray);
}

.section-title {
  font-size: clamp(2rem, 4.5vw, 3.2rem);
  font-weight: 700;
  line-height: 1.15;
  letter-spacing: -0.02em;
  color: var(--cg-white);
  margin-bottom: var(--space-lg);
  max-width: 20ch;
}

/* ----------------------------------------------------------
   6. Expertise
   ---------------------------------------------------------- */
.expertise {
  border-top: var(--border-thin);
}

.expertise-stack {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1px;
  background: var(--cg-darkgray);
  border: var(--border-thin);
}

.expertise-card {
  background: var(--cg-offblack);
  padding: var(--space-lg) var(--space-md);
  transition: background 0.25s ease;
  cursor: default;
}

.expertise-card:hover,
.expertise-card:focus-within {
  background: var(--cg-dark);
}

.card-index {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--cg-gold);
  margin-bottom: var(--space-sm);
  letter-spacing: 0.06em;
}

.card-title {
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--cg-white);
  margin-bottom: var(--space-sm);
  letter-spacing: -0.01em;
}

.card-body {
  font-size: 0.95rem;
  line-height: 1.7;
  color: var(--cg-offwhite);
  margin-bottom: var(--space-md);
}

.card-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.card-tags li {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 500;
  letter-spacing: 0.04em;
  color: var(--cg-midgray);
  padding: 0.25rem 0.65rem;
  border: 1px solid var(--cg-darkgray);
  border-radius: 3px;
}

/* ----------------------------------------------------------
   7. Metrics
   ---------------------------------------------------------- */
.metrics {
  border-top: var(--border-thin);
}

.metrics-display {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-md);
}

.metric-item {
  position: relative;
}

.metric-value {
  font-family: var(--font-mono);
  font-size: clamp(2.2rem, 5vw, 3.6rem);
  font-weight: 700;
  color: var(--cg-gold);
  line-height: 1;
  letter-spacing: -0.02em;
  font-variant-numeric: tabular-nums;
}

.metric-label {
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--cg-gray);
  margin-top: 0.5rem;
  letter-spacing: 0.01em;
}

.metric-rule {
  width: 2rem;
  height: 2px;
  background: var(--cg-darkgray);
  margin-top: var(--space-sm);
}

/* ----------------------------------------------------------
   8. Contact
   ---------------------------------------------------------- */
.contact {
  border-top: var(--border-thin);
}

.contact-layout {
  display: grid;
  grid-template-columns: 1fr 1.5fr;
  gap: var(--space-xl);
  align-items: start;
}

.contact-lede {
  font-size: 1.05rem;
  line-height: 1.7;
  color: var(--cg-offwhite);
  margin-bottom: var(--space-lg);
  max-width: 40ch;
}

.contact-address {
  font-style: normal;
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.address-block {
  font-size: 0.9rem;
  line-height: 1.7;
  color: var(--cg-gray);
}

.address-block strong {
  color: var(--cg-white);
  font-weight: 600;
  display: block;
  margin-bottom: 0.25rem;
}

.contact-link {
  color: var(--cg-gold);
  font-weight: 500;
  transition: color 0.2s ease;
}

.contact-link:hover {
  color: var(--cg-gold-bright);
}

/* Form */
.contact-form {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.form-label {
  font-size: 0.8rem;
  font-weight: 500;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--cg-gray);
}

.form-input {
  width: 100%;
  padding: 0.75rem 1rem;
  background: var(--cg-offblack);
  border: 1px solid var(--cg-darkgray);
  border-radius: 4px;
  font-size: 0.95rem;
  color: var(--cg-white);
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.form-input:focus {
  border-color: var(--cg-gold);
  box-shadow: 0 0 0 3px rgba(240, 192, 64, 0.15);
  outline: none;
}

.form-input.input-error {
  border-color: var(--cg-red);
}

.form-textarea {
  resize: vertical;
  min-height: 8rem;
}

.form-error {
  font-size: 0.8rem;
  color: var(--cg-red);
  font-weight: 500;
  min-height: 1.2em;
}

.form-success {
  padding: var(--space-sm);
  background: var(--cg-offblack);
  border: 1px solid var(--cg-gold-deep);
  border-radius: 4px;
  color: var(--cg-gold);
  font-weight: 500;
  font-size: 0.9rem;
  text-align: center;
}

.form-success[hidden] {
  display: none;
}

.btn-submit {
  align-self: flex-start;
  min-width: 10rem;
}

/* ----------------------------------------------------------
   9. Footer
   ---------------------------------------------------------- */
.site-footer {
  border-top: var(--border-thin);
  padding: var(--space-xl) var(--space-md) var(--space-md);
  max-width: 1100px;
  margin: 0 auto;
}

.footer-grid {
  display: grid;
  grid-template-columns: 1fr 1.5fr;
  gap: var(--space-xl);
  margin-bottom: var(--space-lg);
}

.footer-brand .logo-mark {
  margin-bottom: var(--space-sm);
}

.footer-tagline {
  font-size: 0.85rem;
  color: var(--cg-midgray);
  line-height: 1.6;
  max-width: 30ch;
}

.footer-links {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-md);
}

.footer-col-title {
  display: block;
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--cg-white);
  margin-bottom: var(--space-sm);
}

.footer-col ul {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.footer-col a {
  font-size: 0.85rem;
  color: var(--cg-gray);
  transition: color 0.2s ease;
}

.footer-col a:hover {
  color: var(--cg-gold);
}

.footer-bottom {
  padding-top: var(--space-md);
  border-top: var(--border-thin);
  font-size: 0.75rem;
  color: var(--cg-midgray);
}

/* ----------------------------------------------------------
   10. Legal Pages (Privacy / Terms)
   ---------------------------------------------------------- */
.legal-main {
  padding-top: calc(var(--header-h) + var(--space-xl));
  padding-bottom: var(--space-2xl);
}

.legal-article {
  max-width: 740px;
  margin: 0 auto;
  padding: 0 var(--space-md);
}

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

.legal-header .section-overline {
  margin-bottom: var(--space-sm);
}

.legal-header .section-overline .overline-num {
  color: var(--cg-gold);
  font-size: 0.7rem;
}

.legal-header h1 {
  font-size: clamp(2rem, 5vw, 3.5rem);
  font-weight: 700;
  color: var(--cg-white);
  letter-spacing: -0.02em;
  line-height: 1.15;
  margin-bottom: var(--space-sm);
}

.legal-effective {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--cg-midgray);
  letter-spacing: 0.03em;
}

.legal-body section {
  padding: 0;
  margin-bottom: var(--space-lg);
  max-width: none;
}

.legal-body h2 {
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--cg-white);
  margin-bottom: var(--space-sm);
  letter-spacing: -0.01em;
  padding-top: var(--space-md);
  border-top: var(--border-thin);
}

.legal-body h3 {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--cg-offwhite);
  margin-top: var(--space-md);
  margin-bottom: var(--space-sm);
}

.legal-body p {
  margin-bottom: var(--space-sm);
  color: var(--cg-offwhite);
  line-height: 1.75;
}

.legal-body ul {
  list-style: disc;
  padding-left: 1.5rem;
  margin-bottom: var(--space-sm);
}

.legal-body li {
  margin-bottom: 0.4rem;
  color: var(--cg-offwhite);
  line-height: 1.65;
}

.legal-body strong {
  color: var(--cg-white);
  font-weight: 600;
}

/* ----------------------------------------------------------
   11. Scroll Animations
   ---------------------------------------------------------- */
.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.7s var(--ease-out), transform 0.7s var(--ease-out);
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

.slide-up {
  opacity: 0;
  transform: translateY(40px);
  transition: opacity 0.6s var(--ease-out), transform 0.6s var(--ease-out);
}

.slide-up.visible {
  opacity: 1;
  transform: translateY(0);
}

/* Stagger children */
.stagger-children > * {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.5s var(--ease-out), transform 0.5s var(--ease-out);
}

.stagger-children > *.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ----------------------------------------------------------
   12. Responsive
   ---------------------------------------------------------- */

/* Tablet */
@media (max-width: 900px) {
  :root {
    --space-2xl: 6rem;
    --space-xl: 4rem;
    --space-lg: 2.5rem;
  }

  .expertise-stack {
    grid-template-columns: 1fr;
  }

  .metrics-display {
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-lg);
  }

  .contact-layout {
    grid-template-columns: 1fr;
    gap: var(--space-lg);
  }

  .footer-grid {
    grid-template-columns: 1fr;
    gap: var(--space-lg);
  }

  .footer-links {
    grid-template-columns: repeat(3, 1fr);
  }

  .billboard-headline {
    font-size: clamp(2rem, 8vw, 3.5rem);
  }
}

/* Mobile */
@media (max-width: 640px) {
  :root {
    --space-2xl: 4rem;
    --space-xl: 3rem;
    --space-lg: 2rem;
    --space-md: 1.25rem;
    --header-h: 3.75rem;
  }

  /* Mobile Nav */
  .nav-toggle {
    display: flex;
  }

  .nav-menu {
    position: fixed;
    top: 0;
    right: 0;
    width: 280px;
    height: 100vh;
    height: 100dvh;
    flex-direction: column;
    justify-content: center;
    align-items: flex-start;
    gap: 0;
    background: var(--cg-offblack);
    border-left: var(--border-thin);
    padding: var(--space-xl) var(--space-md);
    transform: translateX(100%);
    transition: transform 0.35s var(--ease-out);
    z-index: 5;
  }

  .nav-menu.nav-open {
    transform: translateX(0);
  }

  .nav-link {
    font-size: 1.1rem;
    padding: 0.75rem 0;
    width: 100%;
    border-bottom: var(--border-thin);
  }

  /* Mobile overlay */
  .nav-menu::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background: rgba(0, 0, 0, 0.6);
    z-index: -1;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.3s ease;
  }

  .nav-menu.nav-open::before {
    opacity: 1;
    pointer-events: auto;
  }

  .metrics-display {
    grid-template-columns: 1fr 1fr;
    gap: var(--space-md);
  }

  .metric-value {
    font-size: 2rem;
  }

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

  .btn-primary,
  .btn-ghost {
    justify-content: center;
  }

  .footer-links {
    grid-template-columns: 1fr 1fr;
    gap: var(--space-md);
  }

  .legal-article {
    padding: 0 var(--space-sm);
  }

  .legal-body h2 {
    font-size: 1.2rem;
  }
}

/* Small mobile */
@media (max-width: 400px) {
  :root {
    --space-lg: 1.5rem;
  }

  .metrics-display {
    grid-template-columns: 1fr;
  }

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

  .card-tags {
    gap: 0.35rem;
  }
}

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

  .fade-in,
  .slide-up,
  .stagger-children > * {
    transition: none;
    opacity: 1;
    transform: none;
  }

  .nav-menu {
    transition: none;
  }

  .billboard-marquee span {
    animation: none;
  }
}

/* ----------------------------------------------------------
   14. Print
   ---------------------------------------------------------- */
@media print {
  body {
    background: #fff;
    color: #000;
  }

  .site-header,
  .site-footer,
  .nav-toggle,
  .billboard-marquee {
    display: none;
  }

  .billboard,
  section {
    padding: 1rem 0;
  }

  a {
    color: #000;
    text-decoration: underline;
  }
}