/* ===== Fonts ===== */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600&family=Noto+Serif+SC:wght@400;600;700&family=JetBrains+Mono:wght@400;500&display=swap');

/* ===== CSS Variables — New Chinese Ink Wash ===== */
:root {
  --font-display: 'Noto Serif SC', serif;
  --font-body: 'Inter', sans-serif;
  --font-mono: 'JetBrains Mono', monospace;

  --color-bg: #F5F0E8;
  --color-surface: rgba(255, 255, 255, 0.65);
  --color-text: #2C2C28;
  --color-text-secondary: #6B6B66;
  --color-text-muted: #9C9C96;
  --color-heading: #1C1C1A;
  --color-accent: #8DB5A4;
  --color-accent-hover: #6B9B88;
  --color-accent-soft: rgba(141, 181, 164, 0.12);
  --color-accent-deep: #5B8C6F;
  --color-vermillion: #C23B22;
  --color-ink-divider: rgba(44, 44, 40, 0.07);
  --color-header-border: rgba(44, 44, 40, 0.06);
  --color-footer-text: #9C9C96;
  --color-btn-primary-text: #F5F0E8;

  --radius-sm: 4px;
  --radius-md: 6px;
  --radius-lg: 8px;
  --radius-xl: 12px;
  --radius-full: 9999px;

  --shadow-card: 0 1px 3px rgba(44, 44, 40, 0.04);
  --shadow-card-hover: 0 4px 12px rgba(44, 44, 40, 0.06);
}

[data-theme="dark"] {
  --color-bg: #1A1A18;
  --color-surface: rgba(255, 255, 255, 0.04);
  --color-text: #E8E4DC;
  --color-text-secondary: #8C8C88;
  --color-text-muted: #6B6B66;
  --color-heading: #F0ECE4;
  --color-accent: #8DB5A4;
  --color-accent-hover: #A8C5B8;
  --color-accent-soft: rgba(141, 181, 164, 0.1);
  --color-ink-divider: rgba(232, 228, 220, 0.06);
  --color-header-border: rgba(232, 228, 220, 0.05);
  --color-footer-text: #6B6B66;
  --color-btn-primary-text: #1A1A18;
  --shadow-card: 0 1px 3px rgba(0, 0, 0, 0.15);
  --shadow-card-hover: 0 4px 12px rgba(0, 0, 0, 0.2);
}

/* ===== Reset ===== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-body);
  font-size: 1rem;
  line-height: 1.7;
  color: var(--color-text);
  background: var(--color-bg);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background 0.4s ease, color 0.4s ease;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* ===== Ink Wash Background ===== */
.ambient-bg {
  position: fixed;
  inset: 0;
  z-index: -1;
  pointer-events: none;
  background-color: var(--color-bg);
  background-image:
    radial-gradient(ellipse 65% 40% at 10% 8%, rgba(141, 181, 164, 0.06) 0%, transparent 60%),
    radial-gradient(ellipse 35% 45% at 90% 85%, rgba(44, 44, 40, 0.025) 0%, transparent 50%);
  transition: background 0.4s ease;
}

[data-theme="dark"] .ambient-bg {
  background-image:
    radial-gradient(ellipse 65% 40% at 10% 8%, rgba(141, 181, 164, 0.04) 0%, transparent 60%),
    radial-gradient(ellipse 35% 45% at 90% 85%, rgba(232, 228, 220, 0.015) 0%, transparent 50%);
}

/* ===== Header ===== */
header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: transparent;
  padding: 0.75rem 2rem;
  height: 72px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: all 0.3s ease;
}

header.scrolled {
  background: var(--color-surface);
  -webkit-backdrop-filter: blur(20px);
  backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--color-header-border);
  padding: 0.5rem 2rem;
  height: 64px;
}

.header-left {
  display: flex;
  align-items: center;
  gap: 2.5rem;
}

.logo {
  font-family: var(--font-display);
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--color-heading);
  text-decoration: none;
  transition: color 0.2s;
  letter-spacing: 0.05em;
}

.logo:hover {
  color: var(--color-accent);
}

nav {
  display: flex;
  align-items: center;
  gap: 0.15rem;
}

nav a {
  color: var(--color-text-secondary);
  text-decoration: none;
  font-size: 0.85rem;
  font-weight: 500;
  padding: 0.4rem 0.85rem;
  border-radius: var(--radius-sm);
  transition: color 0.2s, background 0.2s;
  letter-spacing: 0.02em;
}

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

/* Active nav — approximate with current page */
nav a[aria-current="page"] {
  color: var(--color-accent-deep);
}

/* ===== Theme Toggle ===== */
.theme-toggle {
  background: var(--color-surface);
  -webkit-backdrop-filter: blur(12px);
  backdrop-filter: blur(12px);
  border: 1px solid var(--color-ink-divider);
  color: var(--color-text-secondary);
  cursor: pointer;
  width: 38px;
  height: 38px;
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.25s;
  font-size: 1rem;
  line-height: 1;
}

.theme-toggle:hover {
  color: var(--color-accent);
  border-color: var(--color-accent);
  background: var(--color-accent-soft);
}

.icon-light { display: none; }
.icon-dark { display: inline; }
[data-theme="dark"] .icon-light { display: inline; }
[data-theme="dark"] .icon-dark { display: none; }

/* ===== Main ===== */
main {
  flex: 1;
  width: 100%;
}

/* ===== Hero ===== */
.hero {
  min-height: calc(100vh - 72px);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 2rem 1.5rem;
  position: relative;
  overflow: hidden;
}

/* Decorative large "易" character in background */
.hero::before {
  content: '易';
  position: absolute;
  font-family: var(--font-display);
  font-size: clamp(18rem, 40vw, 36rem);
  font-weight: 700;
  color: var(--color-ink-divider);
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  pointer-events: none;
  line-height: 1;
  user-select: none;
  opacity: 0.5;
}

.hero-card {
  position: relative;
  z-index: 1;
  text-align: center;
  max-width: 520px;
  width: 100%;
  padding: 2.5rem;
}

.hero-symbol {
  font-size: 2.5rem;
  line-height: 1;
  margin-bottom: 1rem;
  color: var(--color-accent);
  opacity: 0.7;
}

.hero-tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--color-accent-deep);
  padding: 0.25rem 0.9rem;
  border: 1px solid var(--color-ink-divider);
  border-radius: var(--radius-full);
  margin-bottom: 1.5rem;
  font-family: var(--font-body);
}

.ink-dot {
  width: 4px;
  height: 4px;
  border-radius: 50%;
  background: var(--color-accent);
}

.hero-title {
  font-family: var(--font-display);
  font-size: clamp(2.5rem, 6vw, 4rem);
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: 0.02em;
  color: var(--color-heading);
  margin-bottom: 1rem;
}

.hero-title .text-ink {
  color: var(--color-accent-deep);
}

.hero-desc {
  font-size: 0.95rem;
  color: var(--color-text-secondary);
  max-width: 340px;
  margin: 0 auto 2rem;
  line-height: 1.8;
  letter-spacing: 0.04em;
}

.hero-actions {
  display: flex;
  gap: 0.75rem;
  flex-wrap: wrap;
  justify-content: center;
}

/* Decorative trigram row */
.hero-trigrams {
  display: flex;
  justify-content: center;
  gap: 0.6rem;
  margin-top: 2.5rem;
  font-size: 1.1rem;
  color: var(--color-text-muted);
  opacity: 0.35;
  letter-spacing: 0.2em;
}

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.65rem 1.5rem;
  border-radius: var(--radius-sm);
  font-family: var(--font-body);
  font-size: 0.85rem;
  font-weight: 500;
  text-decoration: none;
  cursor: pointer;
  border: none;
  transition: all 0.3s ease;
  line-height: 1.4;
  letter-spacing: 0.04em;
}

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

.btn-primary:hover {
  background: var(--color-accent-hover);
  transform: translateY(-1px);
}

.btn-outline {
  background: transparent;
  color: var(--color-text-secondary);
  border: 1px solid var(--color-ink-divider);
}

.btn-outline:hover {
  color: var(--color-heading);
  border-color: var(--color-text-muted);
  background: var(--color-surface);
  transform: translateY(-1px);
}

.btn svg {
  width: 15px;
  height: 15px;
}

/* ===== Section Common ===== */
.section {
  padding: 5rem 1.5rem;
}

.section-inner {
  max-width: 800px;
  margin: 0 auto;
}

.section-label {
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--color-accent-deep);
  margin-bottom: 0.5rem;
  font-family: var(--font-body);
}

.section-label-vert {
  writing-mode: vertical-rl;
  position: absolute;
  left: -2rem;
  top: 0.25rem;
  font-size: 0.65rem;
  letter-spacing: 0.2em;
  color: var(--color-text-muted);
  opacity: 0.5;
}

.section-title {
  font-family: var(--font-display);
  font-size: clamp(1.6rem, 3.5vw, 2.2rem);
  font-weight: 600;
  letter-spacing: 0.03em;
  color: var(--color-heading);
  margin-bottom: 0.75rem;
}

.section-desc {
  font-size: 0.95rem;
  color: var(--color-text-secondary);
  max-width: 480px;
  margin-bottom: 3rem;
  line-height: 1.8;
}

/* ===== Cards Grid (三易) ===== */
.cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1.5rem;
}

.card {
  position: relative;
  background: var(--color-surface);
  border: 1px solid var(--color-ink-divider);
  border-radius: var(--radius-lg);
  padding: 2rem 1.75rem;
  box-shadow: var(--shadow-card);
  transition: all 0.4s ease;
  cursor: default;
}

.card:hover {
  border-color: var(--color-accent);
  box-shadow: var(--shadow-card-hover);
  transform: translateY(-2px);
  background: var(--color-accent-soft);
}

.card-trigram {
  font-size: 1.6rem;
  line-height: 1;
  margin-bottom: 1rem;
  color: var(--color-accent-deep);
  opacity: 0.6;
  transition: opacity 0.3s ease;
}

.card:hover .card-trigram {
  opacity: 1;
}

.card h3 {
  font-family: var(--font-display);
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--color-heading);
  margin-bottom: 0.5rem;
  letter-spacing: 0.02em;
}

.card p {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  line-height: 1.75;
}

/* ===== Ink Divider ===== */
.ink-divider {
  width: 100%;
  height: 1px;
  background: linear-gradient(
    to right,
    transparent 0%,
    var(--color-ink-divider) 15%,
    var(--color-ink-divider) 85%,
    transparent 100%
  );
  margin: 0;
}

/* ===== CTA Section ===== */
.cta-section {
  text-align: center;
  padding: 5rem 1.5rem;
}

.cta-card {
  max-width: 440px;
  margin: 0 auto;
  padding: 2.5rem 2rem;
}

.cta-card h2 {
  font-family: var(--font-display);
  font-size: clamp(1.4rem, 3vw, 1.8rem);
  font-weight: 600;
  letter-spacing: 0.03em;
  color: var(--color-heading);
  margin-bottom: 0.5rem;
}

.cta-card p {
  color: var(--color-text-secondary);
  font-size: 0.9rem;
  margin-bottom: 1.5rem;
}

/* ===== Page Header (subpages) ===== */
.page-header {
  padding: 5rem 1.5rem 3rem;
  text-align: center;
  position: relative;
}

.page-header::before {
  content: '易';
  position: absolute;
  font-family: var(--font-display);
  font-size: clamp(12rem, 25vw, 20rem);
  font-weight: 700;
  color: var(--color-ink-divider);
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  pointer-events: none;
  line-height: 1;
  user-select: none;
  opacity: 0.4;
}

.page-header > * {
  position: relative;
  z-index: 1;
}

.page-header h2 {
  font-family: var(--font-display);
  font-size: clamp(1.8rem, 4vw, 2.5rem);
  font-weight: 600;
  letter-spacing: 0.03em;
  color: var(--color-heading);
  margin-bottom: 0.75rem;
}

.page-header p {
  font-size: 0.95rem;
  color: var(--color-text-secondary);
  max-width: 420px;
  margin: 0 auto;
  line-height: 1.8;
}

/* ===== Content Section (about page) ===== */
.content-section {
  background: var(--color-surface);
  border: 1px solid var(--color-ink-divider);
  border-radius: var(--radius-lg);
  padding: 2rem 2rem;
  margin-bottom: 1.5rem;
  box-shadow: var(--shadow-card);
  transition: border-color 0.3s ease, box-shadow 0.3s ease;
  position: relative;
}

.content-section:last-child {
  margin-bottom: 0;
}

.content-section:hover {
  border-color: var(--color-accent);
  box-shadow: var(--shadow-card-hover);
}

.content-section h3 {
  font-family: var(--font-display);
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--color-heading);
  margin-bottom: 0.75rem;
  letter-spacing: 0.02em;
}

.content-section p {
  color: var(--color-text-secondary);
  line-height: 1.85;
  font-size: 0.92rem;
}

.content-section:not(:last-child)::after {
  content: '';
  display: block;
  height: 1px;
  background: linear-gradient(
    to right,
    transparent 0%,
    var(--color-ink-divider) 20%,
    var(--color-ink-divider) 80%,
    transparent 100%
  );
  margin-top: 1.75rem;
}

/* ===== Contact Form ===== */
.contact-form-wrap {
  max-width: 480px;
  margin: 0 auto;
}

.contact-form {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
}

.form-group label {
  font-size: 0.82rem;
  font-weight: 500;
  color: var(--color-heading);
  letter-spacing: 0.03em;
}

.form-group input,
.form-group textarea {
  font-family: var(--font-body);
  font-size: 0.92rem;
  padding: 0.7rem 0.9rem;
  border: 1px solid var(--color-ink-divider);
  border-radius: var(--radius-sm);
  background: var(--color-surface);
  color: var(--color-text);
  transition: all 0.25s;
  outline: none;
}

.form-group input:focus,
.form-group textarea:focus {
  border-color: var(--color-accent);
  box-shadow: 0 0 0 2px var(--color-accent-soft);
  background: var(--color-surface);
}

.form-group input::placeholder,
.form-group textarea::placeholder {
  color: var(--color-text-muted);
  font-weight: 400;
}

.form-group textarea {
  resize: vertical;
  min-height: 100px;
}

.form-feedback {
  padding: 0.65rem 0.9rem;
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  font-weight: 500;
  text-align: center;
}

.form-feedback.success {
  background: var(--color-accent-soft);
  color: var(--color-accent-deep);
}

.form-feedback.error {
  background: rgba(194, 59, 34, 0.08);
  color: var(--color-vermillion);
}

/* ===== Footer ===== */
footer {
  text-align: center;
  padding: 2rem;
  font-size: 0.82rem;
  color: var(--color-footer-text);
  letter-spacing: 0.04em;
}

footer::before {
  content: '';
  display: block;
  width: 60%;
  max-width: 200px;
  height: 1px;
  background: linear-gradient(
    to right,
    transparent 0%,
    var(--color-ink-divider) 50%,
    transparent 100%
  );
  margin: 0 auto 1.5rem;
}

/* ===== Animations ===== */
.animate {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.7s ease,
              transform 0.7s ease;
}

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

.animate-delay-1 { transition-delay: 0.08s; }
.animate-delay-2 { transition-delay: 0.16s; }
.animate-delay-3 { transition-delay: 0.24s; }
.animate-delay-4 { transition-delay: 0.32s; }

/* ===== Responsive ===== */
@media (max-width: 640px) {
  header {
    padding: 0.75rem 1rem;
  }

  header.scrolled {
    padding: 0.5rem 1rem;
  }

  .header-left {
    gap: 1rem;
  }

  nav {
    gap: 0;
  }

  nav a {
    font-size: 0.78rem;
    padding: 0.35rem 0.5rem;
  }

  .hero-card {
    padding: 1.5rem 1rem;
  }

  .hero-trigrams {
    font-size: 0.9rem;
    gap: 0.4rem;
    flex-wrap: wrap;
  }

  .section {
    padding: 3rem 1rem;
  }

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

  .cta-section {
    padding: 3rem 1rem;
  }

  .page-header {
    padding: 3rem 1rem 2rem;
  }

  .content-section {
    padding: 1.5rem;
  }

  .contact-form-wrap {
    max-width: 100%;
  }
}

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

  .animate {
    opacity: 1;
    transform: none;
    transition: none;
  }

  .card, .btn, .theme-toggle, header {
    transition: none;
  }

  .card:hover {
    transform: none;
  }

  .btn:hover {
    transform: none;
  }
}