/* ============================================================
   TanShuai — Computer Systems Design & Related Services
   Unique palette: deep ink navy + coral + mint
   ============================================================ */

:root {
  --bg: #0B0F17;
  --bg-soft: #0F1522;
  --surface: #141B2B;
  --surface-2: #1A2235;
  --line: #232D42;
  --text: #EAF0F8;
  --muted: #9AA6B8;
  --muted-2: #6E7B90;
  --accent: #FF5C4D;
  --accent-soft: #FF8A7D;
  --accent-2: #3DDC97;
  --accent-2-soft: #7CE9BD;
  --radius: 14px;
  --radius-lg: 22px;
  --shadow: 0 20px 50px rgba(0, 0, 0, 0.45);
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

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

a {
  color: var(--accent);
  text-decoration: none;
  transition: color 0.2s ease;
}

a:hover {
  color: var(--accent-soft);
}

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

h1, h2, h3, h4 {
  line-height: 1.2;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.container {
  width: 100%;
  max-width: 1180px;
  margin: 0 auto;
  padding: 0 28px;
}

/* ---------- Navigation (top-centered inline logo) ---------- */
.site-nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: rgba(11, 15, 23, 0.96);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(10px);
}

.site-nav-inner {
  max-width: 1240px;
  margin: 0 auto;
  padding: 16px 28px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
}

.site-nav .brand {
  font-size: 1.4rem;
  font-weight: 800;
  color: var(--text);
  letter-spacing: -0.03em;
  white-space: nowrap;
}

.site-nav .brand .brand-dot {
  color: var(--accent);
}

.nav-group {
  display: flex;
  align-items: center;
  gap: 26px;
  list-style: none;
}

.nav-group a {
  color: var(--muted);
  font-size: 0.95rem;
  font-weight: 500;
}

.nav-group a:hover {
  color: var(--text);
}

.nav-cta {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background-color: var(--accent);
  color: #0B0F17;
  font-weight: 700;
  padding: 10px 20px;
  border-radius: 999px;
  font-size: 0.92rem;
  white-space: nowrap;
}

.nav-cta:hover {
  background-color: var(--accent-soft);
  color: #0B0F17;
}

.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  flex-direction: column;
  gap: 5px;
  padding: 6px;
}

.nav-toggle span {
  display: block;
  width: 26px;
  height: 2.5px;
  background-color: var(--text);
  border-radius: 2px;
}

/* ---------- Hero band (full-bleed overlay) ---------- */
.hero-band {
  position: relative;
  padding: 170px 0 90px;
  background:
    radial-gradient(circle at 82% 18%, rgba(255, 92, 77, 0.20), transparent 42%),
    radial-gradient(circle at 12% 82%, rgba(61, 220, 151, 0.16), transparent 45%),
    linear-gradient(180deg, #0D1320 0%, #0B0F17 100%);
  border-bottom: 1px solid var(--line);
  overflow: hidden;
}

.hero-band::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(35, 45, 66, 0.35) 1px, transparent 1px),
    linear-gradient(90deg, rgba(35, 45, 66, 0.35) 1px, transparent 1px);
  background-size: 56px 56px;
  pointer-events: none;
}

.hero-band .container {
  position: relative;
  z-index: 2;
}

.hero-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  color: var(--accent-2);
  font-weight: 700;
  font-size: 0.85rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  margin-bottom: 22px;
}

.hero-eyebrow::before {
  content: "";
  width: 34px;
  height: 2px;
  background-color: var(--accent-2);
}

.hero-band h1 {
  font-size: clamp(2.4rem, 5.4vw, 4.2rem);
  max-width: 820px;
  margin-bottom: 26px;
}

.hero-band h1 .accent {
  color: var(--accent);
}

.hero-lead {
  font-size: 1.18rem;
  color: var(--muted);
  max-width: 660px;
  margin-bottom: 36px;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  margin-bottom: 56px;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 14px 26px;
  border-radius: 12px;
  font-weight: 700;
  font-size: 1rem;
  cursor: pointer;
  transition: transform 0.2s ease, background-color 0.2s ease, color 0.2s ease;
}

.btn:hover {
  transform: translateY(-2px);
}

.btn-primary {
  background-color: var(--accent);
  color: #0B0F17;
}

.btn-primary:hover {
  background-color: var(--accent-soft);
  color: #0B0F17;
}

.btn-ghost {
  background-color: transparent;
  color: var(--text);
  border: 1px solid var(--line);
}

.btn-ghost:hover {
  border-color: var(--accent-2);
  color: var(--accent-2);
}

.hero-stats {
  display: flex;
  flex-wrap: wrap;
  gap: 48px;
  padding-top: 34px;
  border-top: 1px solid var(--line);
}

.hero-stat .stat-num {
  font-size: 2.4rem;
  font-weight: 800;
  color: var(--text);
  letter-spacing: -0.03em;
}

.hero-stat .stat-num .stat-suffix {
  color: var(--accent-2);
}

.hero-stat .stat-label {
  color: var(--muted-2);
  font-size: 0.9rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

/* ---------- Pillars (big numerals) ---------- */
.pillars-section {
  padding: 100px 0;
  background-color: var(--bg);
}

.section-head {
  max-width: 680px;
  margin-bottom: 56px;
}

.section-kicker {
  color: var(--accent);
  font-weight: 700;
  font-size: 0.85rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  margin-bottom: 14px;
}

.section-head h2 {
  font-size: clamp(1.8rem, 3.4vw, 2.7rem);
  margin-bottom: 16px;
}

.section-head p {
  color: var(--muted);
  font-size: 1.08rem;
}

.pillars-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 26px;
}

.pillar-card {
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 38px 32px;
  transition: transform 0.25s ease, border-color 0.25s ease;
}

.pillar-card:hover {
  transform: translateY(-6px);
  border-color: var(--accent);
}

.pillar-num {
  font-size: 3.4rem;
  font-weight: 800;
  line-height: 1;
  color: transparent;
  -webkit-text-stroke: 1.5px var(--accent-2);
  margin-bottom: 20px;
}

.pillar-card h3 {
  font-size: 1.4rem;
  margin-bottom: 14px;
}

.pillar-card p {
  color: var(--muted);
}

/* ---------- Method timeline ---------- */
.method-section {
  padding: 100px 0;
  background-color: var(--bg-soft);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.timeline {
  position: relative;
  margin-top: 60px;
  padding-left: 40px;
}

.timeline::before {
  content: "";
  position: absolute;
  left: 8px;
  top: 6px;
  bottom: 6px;
  width: 2px;
  background: linear-gradient(var(--accent), var(--accent-2));
}

.timeline-item {
  position: relative;
  padding-bottom: 48px;
  padding-left: 28px;
}

.timeline-item:last-child {
  padding-bottom: 0;
}

.timeline-item::before {
  content: "";
  position: absolute;
  left: -40px;
  top: 8px;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background-color: var(--bg-soft);
  border: 3px solid var(--accent);
}

.timeline-phase {
  color: var(--accent-2);
  font-weight: 700;
  font-size: 0.85rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  margin-bottom: 8px;
}

.timeline-item h3 {
  font-size: 1.5rem;
  margin-bottom: 12px;
}

.timeline-item p {
  color: var(--muted);
  max-width: 720px;
}

/* ---------- About (alternating) ---------- */
.about-section {
  padding: 110px 0;
  background-color: var(--bg);
}

.about-row {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 60px;
  align-items: center;
}

.about-copy h2 {
  font-size: clamp(1.8rem, 3.4vw, 2.7rem);
  margin-bottom: 22px;
}

.about-copy p {
  color: var(--muted);
  margin-bottom: 18px;
}

.about-code {
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 30px;
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 0.9rem;
  line-height: 1.8;
  box-shadow: var(--shadow);
}

.about-code .code-line {
  display: block;
}

.about-code .code-key {
  color: var(--accent-2);
}

.about-code .code-val {
  color: var(--accent-soft);
}

.about-code .code-punct {
  color: var(--muted-2);
}

/* ---------- Capabilities horizontal scroll ---------- */
.capabilities-section {
  padding: 100px 0;
  background-color: var(--bg-soft);
  border-top: 1px solid var(--line);
}

.cap-scroll {
  display: flex;
  gap: 22px;
  overflow-x: auto;
  padding: 8px 4px 24px;
  scrollbar-width: thin;
  scrollbar-color: var(--accent) var(--surface);
}

.cap-scroll::-webkit-scrollbar {
  height: 8px;
}

.cap-scroll::-webkit-scrollbar-thumb {
  background-color: var(--accent);
  border-radius: 4px;
}

.cap-card {
  flex: 0 0 320px;
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 30px;
  transition: border-color 0.2s ease, transform 0.2s ease;
}

.cap-card:hover {
  border-color: var(--accent-2);
  transform: translateY(-4px);
}

.cap-icon {
  font-size: 1.9rem;
  margin-bottom: 16px;
  color: var(--accent-2);
}

.cap-card h3 {
  font-size: 1.25rem;
  margin-bottom: 12px;
}

.cap-card p {
  color: var(--muted);
  font-size: 0.97rem;
}

/* ---------- Why numbered list ---------- */
.why-section {
  padding: 100px 0;
  background-color: var(--bg);
}

.why-list {
  list-style: none;
  counter-reset: why;
  display: grid;
  gap: 20px;
}

.why-item {
  display: flex;
  align-items: flex-start;
  gap: 24px;
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 28px 30px;
}

.why-item::before {
  counter-increment: why;
  content: "0" counter(why);
  font-size: 1.9rem;
  font-weight: 800;
  color: var(--accent);
  line-height: 1;
  min-width: 56px;
}

.why-item h3 {
  font-size: 1.25rem;
  margin-bottom: 8px;
}

.why-item p {
  color: var(--muted);
}

/* ---------- Contact ---------- */
.contact-section {
  padding: 110px 0;
  background:
    radial-gradient(circle at 20% 20%, rgba(61, 220, 151, 0.12), transparent 40%),
    radial-gradient(circle at 88% 80%, rgba(255, 92, 77, 0.14), transparent 42%),
    var(--bg-soft);
  border-top: 1px solid var(--line);
}

.contact-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 60px;
  align-items: start;
}

.contact-info h2 {
  font-size: clamp(1.8rem, 3.4vw, 2.7rem);
  margin-bottom: 20px;
}

.contact-info > p {
  color: var(--muted);
  margin-bottom: 30px;
}

.contact-details {
  list-style: none;
  display: grid;
  gap: 16px;
}

.contact-details li {
  color: var(--text);
}

.contact-details .detail-label {
  display: block;
  color: var(--muted-2);
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 4px;
}

.contact-details a {
  color: var(--text);
  font-weight: 600;
}

.contact-details a:hover {
  color: var(--accent-2);
}

.contact-form {
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 36px;
}

.form-field {
  margin-bottom: 18px;
}

.form-field label {
  display: block;
  color: var(--muted);
  font-size: 0.9rem;
  font-weight: 600;
  margin-bottom: 7px;
}

.form-field input,
.form-field textarea {
  width: 100%;
  background-color: var(--bg);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 13px 15px;
  color: var(--text);
  font-size: 1rem;
  font-family: inherit;
}

.form-field input:focus,
.form-field textarea:focus {
  outline: none;
  border-color: var(--accent-2);
}

.form-field textarea {
  resize: vertical;
  min-height: 130px;
}

.form-note {
  display: none;
  margin-top: 14px;
  padding: 12px 16px;
  border-radius: 10px;
  font-size: 0.95rem;
  font-weight: 600;
}

.form-note.ok {
  display: block;
  background: rgba(61, 220, 151, 0.16);
  color: var(--accent-2-soft);
  border: 1px solid var(--accent-2);
}

/* ---------- Footer ---------- */
.site-footer {
  background-color: #080B12;
  border-top: 1px solid var(--line);
}

.newsletter-band {
  padding: 56px 0;
  border-bottom: 1px solid var(--line);
}

.newsletter-band .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 30px;
  flex-wrap: wrap;
}

.newsletter-band h3 {
  font-size: 1.6rem;
  max-width: 460px;
}

.newsletter-form {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.newsletter-form input {
  background-color: var(--surface);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 13px 16px;
  color: var(--text);
  font-size: 1rem;
  min-width: 260px;
}

.newsletter-form input:focus {
  outline: none;
  border-color: var(--accent);
}

.footer-main {
  padding: 60px 0 30px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 1.6fr 1fr 1fr 1fr;
  gap: 40px;
}

.footer-brand .brand {
  font-size: 1.4rem;
  font-weight: 800;
  color: var(--text);
  margin-bottom: 14px;
}

.footer-brand .brand .brand-dot {
  color: var(--accent);
}

.footer-brand p {
  color: var(--muted);
  font-size: 0.95rem;
  max-width: 320px;
}

.footer-col h4 {
  font-size: 0.9rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--muted-2);
  margin-bottom: 18px;
}

.footer-col ul {
  list-style: none;
  display: grid;
  gap: 11px;
}

.footer-col a {
  color: var(--muted);
  font-size: 0.95rem;
}

.footer-col a:hover {
  color: var(--accent-2);
}

.footer-wordmark {
  padding: 20px 0;
  text-align: center;
  overflow: hidden;
}

.footer-wordmark span {
  font-size: clamp(2.4rem, 9vw, 7rem);
  font-weight: 800;
  letter-spacing: -0.04em;
  color: transparent;
  -webkit-text-stroke: 1px #1F2A40;
  user-select: none;
}

.footer-bottom {
  border-top: 1px solid var(--line);
  padding: 22px 0;
}

.footer-bottom .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}

.footer-bottom p {
  color: var(--muted-2);
  font-size: 0.88rem;
}

/* ---------- Reveal animation ---------- */
.reveal {
  opacity: 0;
  transform: translateY(28px);
  transition: opacity 0.7s ease, transform 0.7s ease;
}

.reveal.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ---------- Responsive ---------- */
@media (max-width: 980px) {
  .pillars-grid {
    grid-template-columns: 1fr;
  }

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

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

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

@media (max-width: 760px) {
  .site-nav-inner {
    flex-wrap: wrap;
  }

  .nav-group {
    width: 100%;
    flex-direction: column;
    align-items: flex-start;
    gap: 0;
    padding: 10px 0;
    display: none;
  }

  .nav-group.open {
    display: flex;
  }

  .nav-group li {
    width: 100%;
    padding: 12px 0;
    border-bottom: 1px solid var(--line);
  }

  .nav-group li:last-child {
    border-bottom: none;
  }

  .nav-cta {
    display: inline-flex;
    margin-top: 12px;
  }

  .nav-toggle {
    display: flex;
  }

  .hero-band {
    padding: 130px 0 70px;
  }

  .hero-stats {
    gap: 28px;
  }

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