/* ============================================================
   XinShengDa — Computer Systems Design & Related Services
   Light water-teal theme
   ============================================================ */

:root {
  --bg: #F4FAFA;
  --surface: #FFFFFF;
  --text: #10333A;
  --teal: #0E9AA7;
  --deep: #0A6B77;
  --aqua: #B8E4E4;
  --aqua-soft: #DDF2F2;
  --sand: #E7D8C3;
  --charcoal: #263238;
  --hairline: #D9E9E9;
  --white: #FFFFFF;
}

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

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: "Segoe UI", "Helvetica Neue", Arial, sans-serif;
  font-size: 16px;
  line-height: 1.7;
  color: var(--text);
  background-color: var(--bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

a {
  color: var(--deep);
  text-decoration: none;
}

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

h1, h2, h3, h4 {
  line-height: 1.2;
  color: var(--text);
  margin: 0 0 0.5em;
}

p {
  margin: 0 0 1em;
}

.container {
  max-width: 1140px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ============================================================
   Buttons
   ============================================================ */
.btn {
  display: inline-block;
  padding: 14px 28px;
  font-size: 16px;
  font-weight: 600;
  line-height: 1.2;
  border-radius: 8px;
  border: 2px solid transparent;
  cursor: pointer;
  text-align: center;
  transition: background-color 0.25s ease, color 0.25s ease,
    border-color 0.25s ease, transform 0.15s ease;
}

.btn:active {
  transform: translateY(1px);
}

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

.btn-primary:hover {
  background-color: var(--deep);
  border-color: var(--deep);
  color: var(--white);
}

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

.btn-outline:hover {
  background-color: var(--deep);
  color: var(--white);
}

.btn-light {
  background-color: var(--white);
  color: var(--deep);
  border-color: var(--white);
}

.btn-light:hover {
  background-color: var(--aqua);
  border-color: var(--aqua);
  color: var(--text);
}

/* ============================================================
   Drop Badge Navigation
   ============================================================ */
.drop-nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: var(--surface);
  border-bottom: 2px solid var(--teal);
  box-shadow: 0 2px 12px rgba(10, 107, 119, 0.08);
}

.drop-nav .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 72px;
}

.drop-nav .brand {
  display: flex;
  align-items: center;
  gap: 10px;
  padding-top: 4px;
}

.water-badge {
  position: relative;
  display: inline-flex;
  margin-top: 7px;
}

.water-badge .tip {
  position: absolute;
  top: -9px;
  left: 50%;
  transform: translateX(-50%);
  width: 0;
  height: 0;
  border-left: 7px solid transparent;
  border-right: 7px solid transparent;
  border-bottom: 11px solid var(--teal);
}

.water-badge .drop {
  width: 30px;
  height: 30px;
  background-color: var(--teal);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text);
  font-weight: 800;
  font-size: 17px;
  line-height: 1;
}

.brand .wordmark {
  font-size: 20px;
  font-weight: 800;
  letter-spacing: 0.04em;
  color: var(--text);
}

.drop-nav .nav-links {
  display: flex;
  align-items: center;
  gap: 30px;
  list-style: none;
  margin: 0;
  padding: 0;
}

.drop-nav .nav-links a {
  position: relative;
  display: inline-block;
  padding: 26px 0 22px;
  color: var(--text);
  font-weight: 600;
  font-size: 15px;
}

.drop-nav .nav-links a:hover {
  color: var(--deep);
}

.drop-nav .nav-links a.active {
  color: var(--deep);
}

.drop-nav .nav-links a.active::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  height: 4px;
  background-color: var(--teal);
  border-radius: 2px 2px 0 0;
}

.nav-cta {
  background-color: var(--teal);
  color: var(--white);
  padding: 10px 20px;
  border-radius: 8px;
  font-weight: 700;
  font-size: 14px;
  white-space: nowrap;
}

.nav-cta:hover {
  background-color: var(--deep);
  color: var(--white);
}

.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
  width: 44px;
  height: 44px;
}

.nav-toggle span {
  display: block;
  width: 24px;
  height: 3px;
  background-color: var(--deep);
  margin: 5px auto;
  border-radius: 2px;
  transition: transform 0.25s ease, opacity 0.25s ease;
}

.nav-toggle.open span:nth-child(1) {
  transform: translateY(8px) rotate(45deg);
}

.nav-toggle.open span:nth-child(2) {
  opacity: 0;
}

.nav-toggle.open span:nth-child(3) {
  transform: translateY(-8px) rotate(-45deg);
}

/* ============================================================
   Filter Column Hero
   ============================================================ */
.filter-hero {
  background-color: var(--bg);
  padding: 72px 0 80px;
}

.filter-hero .container {
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: 56px;
  align-items: center;
}

.eyebrow-chip {
  display: inline-block;
  background-color: var(--aqua);
  color: var(--deep);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  padding: 7px 16px;
  border-radius: 999px;
  margin-bottom: 22px;
}

.hero-headline {
  font-size: 46px;
  font-weight: 800;
  line-height: 1.12;
  color: var(--text);
  letter-spacing: -0.01em;
  margin-bottom: 22px;
}

.hero-headline .accent {
  color: var(--deep);
}

.hero-sub {
  font-size: 18px;
  color: #24505A;
  max-width: 560px;
  margin-bottom: 30px;
}

.hero-ctas {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
}

/* Water filter column visual */
.filter-visual {
  display: flex;
  align-items: flex-start;
  justify-content: center;
  gap: 22px;
}

.filter-stack {
  text-align: center;
}

.filter-drop {
  width: 0;
  height: 0;
  margin: 0 auto;
  border-left: 12px solid transparent;
  border-right: 12px solid transparent;
  border-bottom: 20px solid var(--teal);
}

.filter-column {
  width: 150px;
  height: 300px;
  margin: 0 auto;
  border: 3px solid var(--teal);
  border-top: none;
  border-radius: 0 0 22px 22px;
  overflow: hidden;
  display: flex;
  flex-direction: column;
}

.filter-column .strata {
  flex: 1;
}

.filter-column .gravel {
  background-color: var(--aqua);
}

.filter-column .sand {
  background-color: var(--sand);
}

.filter-column .carbon {
  background-color: var(--charcoal);
}

.filter-column .fine {
  background-color: var(--teal);
}

.filter-outlet {
  width: 16px;
  height: 16px;
  margin: 12px auto 0;
  background-color: var(--deep);
  border-radius: 50%;
}

.filter-labels {
  display: flex;
  flex-direction: column;
  gap: 16px;
  padding-top: 40px;
}

.filter-labels .label {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
  color: var(--deep);
}

.filter-labels .swatch {
  width: 14px;
  height: 14px;
  border-radius: 3px;
  display: inline-block;
}

.swatch.gravel { background-color: var(--aqua); }
.swatch.sand { background-color: var(--sand); }
.swatch.carbon { background-color: var(--charcoal); }
.swatch.fine { background-color: var(--teal); }

/* ============================================================
   Statement Row
   ============================================================ */
.statement-row {
  background-color: var(--surface);
  border-top: 1px solid var(--hairline);
  border-bottom: 1px solid var(--hairline);
  padding: 64px 0;
}

.statement-row .container {
  max-width: 980px;
  text-align: center;
}

.statement-row .statement {
  font-size: 28px;
  font-weight: 700;
  line-height: 1.4;
  color: var(--text);
  margin: 0;
}

.statement-row .statement .accent {
  color: var(--deep);
}

/* ============================================================
   Filter Layers
   ============================================================ */
.filter-layers {
  background-color: var(--bg);
  padding: 84px 0;
}

.filter-layers .container {
  display: grid;
  grid-template-columns: 1fr 1.1fr;
  gap: 56px;
  align-items: center;
}

.layers-stack {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.layer {
  display: flex;
  align-items: center;
  gap: 18px;
  border-radius: 12px;
  padding: 18px 22px;
}

.layer .layer-swatch {
  width: 46px;
  height: 46px;
  border-radius: 10px;
  flex: 0 0 46px;
}

.layer .layer-info {
  display: flex;
  flex-direction: column;
}

.layer .layer-name {
  font-weight: 800;
  font-size: 17px;
  color: var(--text);
}

.layer .layer-role {
  font-size: 14px;
  color: #24505A;
}

.layer.gravel { background-color: var(--aqua); }
.layer.gravel .layer-swatch { background-color: var(--aqua); border: 2px solid var(--deep); }
.layer.sand { background-color: #F4EBDD; }
.layer.sand .layer-swatch { background-color: var(--sand); border: 2px solid #C9B78F; }
.layer.carbon { background-color: #DDE3E6; }
.layer.carbon .layer-swatch { background-color: var(--charcoal); }
.layer.fine { background-color: var(--aqua-soft); }
.layer.fine .layer-swatch { background-color: var(--teal); }

.section-head {
  margin-bottom: 28px;
}

.section-kicker {
  display: inline-block;
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--deep);
  margin-bottom: 10px;
}

.section-head h2 {
  font-size: 34px;
  font-weight: 800;
  letter-spacing: -0.01em;
}

.filter-layers .copy p {
  font-size: 17px;
  color: #24505A;
  margin-bottom: 16px;
}

/* ============================================================
   Param Rows
   ============================================================ */
.param-rows {
  background-color: var(--surface);
  border-top: 1px solid var(--hairline);
  border-bottom: 1px solid var(--hairline);
  padding: 84px 0;
}

.param-rows .container {
  max-width: 900px;
}

.param-row {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 24px;
  padding: 26px 4px;
  border-bottom: 1px solid var(--hairline);
}

.param-row:last-child {
  border-bottom: none;
}

.param-name {
  font-size: 18px;
  font-weight: 700;
  color: var(--text);
}

.param-value {
  font-size: 28px;
  font-weight: 800;
  color: var(--teal);
  text-align: right;
  letter-spacing: -0.01em;
}

.param-note {
  font-size: 14px;
  color: #24505A;
}

/* ============================================================
   Cert Strip
   ============================================================ */
.cert-strip {
  background-color: var(--bg);
  padding: 84px 0;
}

.cert-strip .container {
  text-align: center;
}

.cert-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 28px;
  margin-top: 40px;
}

.cert-badge {
  text-align: center;
}

.cert-square {
  width: 96px;
  height: 96px;
  margin: 0 auto 16px;
  background-color: var(--teal);
  border-radius: 16px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--white);
  font-size: 26px;
  font-weight: 800;
  letter-spacing: 0.02em;
}

.cert-name {
  font-weight: 800;
  font-size: 17px;
  color: var(--text);
  margin-bottom: 4px;
}

.cert-desc {
  font-size: 14px;
  color: #24505A;
  max-width: 220px;
  margin: 0 auto;
}

/* ============================================================
   FAQ Accordion
   ============================================================ */
.faq-section {
  background-color: var(--surface);
  border-top: 1px solid var(--hairline);
  padding: 84px 0;
}

.faq-section .container {
  max-width: 860px;
}

.faq-item {
  border: 1px solid var(--hairline);
  border-radius: 12px;
  margin-bottom: 14px;
  background-color: var(--white);
}

.faq-question {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 20px 24px;
  font-size: 17px;
  font-weight: 700;
  color: var(--text);
  text-align: left;
}

.faq-question:hover {
  color: var(--deep);
}

.faq-icon {
  flex: 0 0 24px;
  width: 24px;
  height: 24px;
  position: relative;
}

.faq-icon::before,
.faq-icon::after {
  content: "";
  position: absolute;
  background-color: var(--teal);
  border-radius: 2px;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

.faq-icon::before {
  width: 16px;
  height: 3px;
}

.faq-icon::after {
  width: 3px;
  height: 16px;
  transition: transform 0.25s ease;
}

.faq-item.open .faq-icon::after {
  transform: translate(-50%, -50%) rotate(90deg);
}

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.35s ease;
}

.faq-answer-inner {
  padding: 0 24px 22px;
  color: #24505A;
}

/* ============================================================
   CTA Band
   ============================================================ */
.cta-band {
  background-color: var(--teal);
  padding: 72px 0;
}

.cta-band .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 32px;
  flex-wrap: wrap;
}

.cta-band h2 {
  color: var(--white);
  font-size: 32px;
  font-weight: 800;
  margin: 0 0 8px;
}

.cta-band p {
  color: var(--aqua-soft);
  margin: 0;
  font-size: 17px;
}

/* ============================================================
   Basin Footer
   ============================================================ */
.basin-footer {
  background-color: var(--surface);
  border-top: 4px solid var(--teal);
  padding-top: 56px;
}

.footer-cols {
  display: grid;
  grid-template-columns: 1.3fr 1fr 1.4fr;
  gap: 40px;
  padding-bottom: 48px;
}

.footer-brand .wordmark {
  font-size: 24px;
  font-weight: 800;
  color: var(--deep);
  margin-bottom: 12px;
}

.footer-brand p {
  color: #24505A;
  font-size: 15px;
  max-width: 300px;
}

.footer-col h4 {
  font-size: 15px;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text);
  margin-bottom: 16px;
}

.footer-col ul {
  list-style: none;
  margin: 0;
  padding: 0;
}

.footer-col ul li {
  margin-bottom: 10px;
}

.footer-col ul a {
  color: #24505A;
  font-size: 15px;
}

.footer-col ul a:hover {
  color: var(--teal);
}

.footer-contact p {
  font-size: 15px;
  color: #24505A;
  margin-bottom: 10px;
}

.footer-contact a {
  color: var(--deep);
  font-weight: 600;
}

.footer-strip {
  background-color: var(--aqua);
  color: var(--text);
  padding: 18px 0;
  font-size: 14px;
}

.footer-strip .container {
  display: flex;
  align-items: center;
  justify-content: center;
  flex-wrap: wrap;
  gap: 8px;
}

.footer-strip a {
  color: var(--deep);
  font-weight: 700;
}

.footer-strip a:hover {
  color: var(--text);
}

.footer-strip .sep {
  color: var(--deep);
}

/* ============================================================
   Scroll reveal
   ============================================================ */
.fade-up {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-up.visible {
  opacity: 1;
  transform: none;
}

/* ============================================================
   Shared page hero (services + contact)
   ============================================================ */
.page-hero {
  background-color: var(--bg);
  padding: 68px 0 60px;
  border-bottom: 1px solid var(--hairline);
}

.page-hero h1 {
  font-size: 44px;
  font-weight: 800;
  letter-spacing: -0.01em;
  margin-bottom: 16px;
}

.page-hero .lead {
  font-size: 18px;
  color: #24505A;
  max-width: 780px;
  margin: 0;
}

/* ============================================================
   Services page
   ============================================================ */
.services-grid-section {
  background-color: var(--surface);
  padding: 84px 0;
}

.services-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 32px;
}

.service-card {
  background-color: var(--white);
  border: 1px solid var(--hairline);
  border-top: 4px solid var(--teal);
  border-radius: 14px;
  padding: 32px 30px;
}

.service-card .service-num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 46px;
  height: 46px;
  border-radius: 12px;
  background-color: var(--aqua);
  color: var(--deep);
  font-weight: 800;
  font-size: 20px;
  margin-bottom: 18px;
}

.service-card h3 {
  font-size: 22px;
  font-weight: 800;
  margin-bottom: 12px;
}

.service-card p {
  color: #24505A;
  margin: 0;
}

.process-overview {
  background-color: var(--bg);
  padding: 84px 0;
}

.process-steps {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 26px;
  margin-top: 44px;
}

.process-step {
  position: relative;
  background-color: var(--white);
  border: 1px solid var(--hairline);
  border-radius: 14px;
  padding: 28px 24px;
}

.process-step .step-num {
  font-size: 14px;
  font-weight: 800;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--deep);
  display: block;
  margin-bottom: 10px;
}

.process-step h4 {
  font-size: 19px;
  font-weight: 800;
  margin-bottom: 10px;
}

.process-step p {
  font-size: 15px;
  color: #24505A;
  margin: 0;
}

/* ============================================================
   Contact page
   ============================================================ */
.contact-section {
  background-color: var(--surface);
  padding: 84px 0;
}

.contact-grid {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 48px;
  align-items: start;
}

.contact-form {
  background-color: var(--white);
  border: 1px solid var(--hairline);
  border-radius: 16px;
  padding: 36px 32px;
}

.contact-form h2 {
  font-size: 26px;
  font-weight: 800;
  margin-bottom: 6px;
}

.contact-form .form-hint {
  color: #24505A;
  font-size: 15px;
  margin-bottom: 24px;
}

.form-group {
  margin-bottom: 20px;
}

.form-group label {
  display: block;
  font-weight: 700;
  font-size: 15px;
  color: var(--text);
  margin-bottom: 7px;
}

.form-group input,
.form-group textarea {
  width: 100%;
  font-family: inherit;
  font-size: 16px;
  color: var(--text);
  background-color: var(--bg);
  border: 1px solid var(--hairline);
  border-radius: 8px;
  padding: 13px 15px;
  transition: border-color 0.2s ease;
}

.form-group input:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--teal);
}

.form-group textarea {
  min-height: 150px;
  resize: vertical;
}

.info-card {
  background-color: var(--white);
  border: 1px solid var(--hairline);
  border-left: 4px solid var(--teal);
  border-radius: 12px;
  padding: 28px 26px;
  margin-bottom: 22px;
}

.info-card h3 {
  font-size: 18px;
  font-weight: 800;
  margin-bottom: 12px;
  color: var(--deep);
}

.info-card p {
  color: #24505A;
  font-size: 15px;
  margin-bottom: 8px;
}

.info-card a {
  color: var(--deep);
  font-weight: 600;
}

.info-card .hours-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.info-card .hours-list li {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  padding: 7px 0;
  border-bottom: 1px solid var(--hairline);
  font-size: 15px;
  color: #24505A;
}

.info-card .hours-list li:last-child {
  border-bottom: none;
}

.info-card .hours-list .day {
  font-weight: 700;
  color: var(--text);
}

/* ============================================================
   Responsive
   ============================================================ */
@media (max-width: 960px) {
  .filter-hero .container {
    grid-template-columns: 1fr;
    gap: 48px;
  }

  .hero-headline {
    font-size: 38px;
  }

  .filter-layers .container {
    grid-template-columns: 1fr;
    gap: 40px;
  }

  .footer-cols {
    grid-template-columns: 1fr;
    gap: 32px;
  }

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

  .process-steps {
    grid-template-columns: 1fr 1fr;
  }

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

@media (max-width: 760px) {
  .drop-nav .container {
    height: 64px;
  }

  .nav-toggle {
    display: block;
  }

  .drop-nav .nav-links {
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    background-color: var(--surface);
    border-bottom: 2px solid var(--teal);
    box-shadow: 0 12px 24px rgba(10, 107, 119, 0.12);
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease;
  }

  .drop-nav .nav-links.open {
    max-height: 420px;
  }

  .drop-nav .nav-links li {
    border-bottom: 1px solid var(--hairline);
  }

  .drop-nav .nav-links a {
    display: block;
    padding: 16px 24px;
  }

  .drop-nav .nav-links a.active::after {
    display: none;
  }

  .drop-nav .nav-links a.active {
    background-color: var(--aqua-soft);
  }

  .nav-cta {
    display: none;
  }

  .hero-headline {
    font-size: 32px;
  }

  .page-hero h1 {
    font-size: 34px;
  }

  .statement-row .statement {
    font-size: 22px;
  }

  .cert-grid {
    grid-template-columns: 1fr;
    gap: 36px;
  }

  .process-steps {
    grid-template-columns: 1fr;
  }

  .param-row {
    flex-direction: column;
    align-items: flex-start;
    gap: 4px;
  }

  .param-value {
    text-align: left;
  }
}