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

:root {
  --color-bg: #fafafa;
  --color-white: #ffffff;
  --color-black: #0a0a0a;
  --color-text: #1a1a1a;
  --color-text-secondary: #6b7280;
  --color-accent: #4f46e5;
  --color-accent-light: #e0e7ff;
  --color-border: #e5e7eb;
  --color-tag-bg: #f3f4f6;
  --font-sans: "Inter", "Noto Sans SC", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --font-serif: "Playfair Display", "Noto Serif SC", Georgia, serif;
  --container-max: 1100px;
  --radius: 12px;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

html { scroll-behavior: smooth; font-size: 16px; }

body {
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

.container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 2rem;
}

/* ===== Navbar ===== */
.navbar {
  position: fixed; top: 0; left: 0; right: 0; z-index: 100;
  background: rgba(250, 250, 250, 0.85);
  backdrop-filter: blur(20px); -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid transparent;
  transition: var(--transition);
}
.navbar.scrolled { border-bottom-color: var(--color-border); }

.nav-inner {
  max-width: var(--container-max); margin: 0 auto; padding: 0 2rem;
  display: flex; align-items: center; justify-content: space-between; height: 72px;
}
.nav-brand {
  font-size: 1.25rem; font-weight: 700; color: var(--color-text);
  text-decoration: none; letter-spacing: -0.02em;
}
.nav-links { display: flex; align-items: center; gap: 2rem; }
.nav-links a {
  text-decoration: none; color: var(--color-text-secondary);
  font-size: 0.9rem; font-weight: 500; transition: var(--transition);
}
.nav-links a:hover { color: var(--color-text); }
.nav-cta {
  background: var(--color-black); color: var(--color-white) !important;
  padding: 0.5rem 1.25rem; border-radius: 100px; font-size: 0.85rem !important;
}
.nav-cta:hover { background: var(--color-accent) !important; }

.nav-toggle {
  display: none; background: none; border: none; cursor: pointer;
  flex-direction: column; gap: 5px; padding: 4px;
}
.nav-toggle span {
  display: block; width: 22px; height: 2px; background: var(--color-text);
  border-radius: 2px; transition: var(--transition);
}
.mobile-menu {
  display: none; position: fixed; top: 72px; left: 0; right: 0;
  background: var(--color-white); border-bottom: 1px solid var(--color-border);
  z-index: 99; padding: 1.5rem 2rem; flex-direction: column; gap: 1rem;
}
.mobile-menu.active { display: flex; }
.mobile-menu a {
  text-decoration: none; color: var(--color-text); font-size: 1.1rem; font-weight: 500;
}

/* ===== Hero ===== */
.hero {
  padding: 8rem 2rem 5rem;
  background: radial-gradient(ellipse 80% 50% at 50% -10%, rgba(79, 70, 229, 0.06), transparent), var(--color-bg);
}
.hero .container {
  display: flex; flex-direction: column; align-items: center; text-align: center;
}
.hero-title {
  font-family: var(--font-serif);
  font-size: clamp(2.25rem, 5.5vw, 3.75rem);
  font-weight: 700; letter-spacing: -0.03em; line-height: 1.15;
  max-width: 750px; margin-bottom: 1rem;
}
.hero-desc {
  font-size: 1.05rem; color: var(--color-text-secondary);
  max-width: 600px; margin-bottom: 3rem; line-height: 1.85;
}

/* ===== Flow ===== */
.flow {
  display: flex; align-items: flex-start; justify-content: center;
  gap: 0; max-width: 900px; margin-bottom: 4rem;
}
.flow-step { flex: 1; text-align: center; padding: 0 0.75rem; position: relative; }
.flow-step:not(:last-child)::after {
  content: "→"; position: absolute; right: -0.5rem; top: 1.2rem;
  font-size: 1.25rem; color: var(--color-border); font-weight: 300;
  transform: translateX(50%);
}
.flow-step-num {
  width: 40px; height: 40px; border-radius: 50%;
  background: var(--color-black); color: var(--color-white);
  display: inline-flex; align-items: center; justify-content: center;
  font-size: 0.85rem; font-weight: 700; margin-bottom: 0.6rem;
}
.flow-step h3 { font-size: 0.92rem; font-weight: 700; margin-bottom: 0.25rem; }
.flow-step p { font-size: 0.8rem; color: var(--color-text-secondary); line-height: 1.5; }

/* ===== Cases ===== */
.cases-section { width: 100%; max-width: 900px; }
.cases-heading {
  font-family: var(--font-serif); font-size: 1.5rem; font-weight: 700;
  letter-spacing: -0.02em; margin-bottom: 1.5rem;
}
.cases-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 1.25rem; }
.case-card {
  background: var(--color-white); border: 1px solid var(--color-border);
  border-radius: var(--radius); padding: 1.5rem; text-align: left;
  transition: var(--transition);
}
.case-card:hover {
  border-color: var(--color-accent-light);
  box-shadow: 0 8px 30px rgba(79, 70, 229, 0.06);
}
.case-card-tag {
  display: inline-block; background: var(--color-tag-bg);
  font-size: 0.72rem; font-weight: 600; color: var(--color-text-secondary);
  padding: 0.15rem 0.55rem; border-radius: 100px; margin-bottom: 0.6rem;
}
.case-card h3 { font-size: 1rem; font-weight: 700; margin-bottom: 0.3rem; }
.case-card-desc {
  font-size: 0.85rem; color: var(--color-text-secondary);
  line-height: 1.6; margin-bottom: 0.75rem;
}
.case-card-result { font-size: 0.85rem; font-weight: 600; color: var(--color-accent); }

/* ===== Section Title ===== */
.section-title {
  font-family: var(--font-serif);
  font-size: clamp(2rem, 4vw, 3rem);
  font-weight: 700; letter-spacing: -0.02em;
  text-align: center; margin-bottom: 0.5rem;
}
.section-subtitle {
  text-align: center; color: var(--color-text-secondary);
  font-size: 1.05rem; margin-bottom: 3rem;
}

/* ===== Mentors Grid ===== */
.mentors { padding: 6rem 0; }

.mentors-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1.25rem;
}

.mentor-card {
  background: var(--color-white);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  overflow: hidden;
  transition: var(--transition);
  cursor: pointer;
}

.mentor-card:hover {
  border-color: var(--color-accent-light);
  box-shadow: 0 8px 24px rgba(79, 70, 229, 0.08);
  transform: translateY(-2px);
}

/* -- Collapsed -- */
.mentor-summary {
  display: flex; flex-direction: column; align-items: center;
  padding: 1.75rem 1.25rem 1.5rem; text-align: center;
}

.mentor-avatar {
  width: 80px; height: 80px; border-radius: 50%; overflow: hidden;
  background: linear-gradient(135deg, #e0e7ff 0%, #f3f4f6 100%);
  display: flex; align-items: center; justify-content: center;
  margin-bottom: 0.75rem;
}
.mentor-avatar img { width: 100%; height: 100%; object-fit: cover; }
.mentor-avatar-letter { font-size: 1.75rem; font-weight: 700; color: var(--color-accent); }

.mentor-name { font-size: 1.05rem; font-weight: 700; margin-bottom: 0.1rem; }
.mentor-role { font-size: 0.78rem; color: var(--color-accent); font-weight: 600; margin-bottom: 0.5rem; }

.mentor-meta {
  font-size: 0.78rem; color: var(--color-text-secondary);
  display: flex; flex-wrap: wrap; gap: 0.3rem; justify-content: center;
}
.mentor-meta span {
  background: var(--color-tag-bg); padding: 0.1rem 0.5rem; border-radius: 100px;
}

.mentor-hint {
  font-size: 0.72rem; color: var(--color-text-secondary);
  margin-top: 0.6rem; opacity: 0; transition: var(--transition);
}
.mentor-card:hover .mentor-hint { opacity: 1; }
.mentor-card.expanded .mentor-hint { display: none; }

/* -- Expanded Detail (inside card, same width) -- */
.mentor-detail {
  max-height: 0; overflow: hidden;
  transition: max-height 0.45s cubic-bezier(0.4, 0, 0.2, 1);
}
.mentor-card.expanded .mentor-detail { max-height: 420px; }

.mentor-detail-inner {
  padding: 0 1.25rem 1.5rem;
  border-top: 1px solid var(--color-border);
}

.detail-oneliner {
  font-size: 0.85rem; color: var(--color-text-secondary);
  line-height: 1.6; padding-top: 1rem; margin-bottom: 0.75rem; text-align: center;
}
.detail-label {
  font-size: 0.7rem; font-weight: 700; color: var(--color-text-secondary);
  text-transform: uppercase; letter-spacing: 0.08em; margin-bottom: 0.35rem;
}

.tool-row { display: flex; align-items: center; gap: 0.4rem; margin-bottom: 0.25rem; }
.tool-name { font-size: 0.72rem; font-weight: 500; min-width: 72px; }
.tool-bar-bg {
  flex: 1; height: 3px; background: var(--color-tag-bg);
  border-radius: 2px; overflow: hidden;
}
.tool-bar-fill {
  height: 100%; border-radius: 2px;
  background: linear-gradient(90deg, var(--color-accent), #a78bfa);
  transition: width 0.8s cubic-bezier(0.4, 0, 0.2, 1);
}
.tool-score { font-size: 0.65rem; font-weight: 600; color: var(--color-text-secondary); min-width: 14px; text-align: right; }

.detail-tools { margin-bottom: 0.6rem; }
.detail-workflows { margin-bottom: 0.6rem; }

.workflow-tags { display: flex; flex-wrap: wrap; gap: 0.25rem; }
.workflow-tag {
  background: var(--color-tag-bg); color: var(--color-text);
  padding: 0.15rem 0.5rem; border-radius: 100px;
  font-size: 0.68rem; font-weight: 500;
}

.detail-footer {
  display: flex; align-items: center; justify-content: space-between;
  padding-top: 0.6rem; border-top: 1px solid var(--color-border);
}
.service-badges { display: flex; gap: 0.25rem; }
.badge { padding: 0.1rem 0.4rem; border-radius: 100px; font-size: 0.65rem; font-weight: 600; }
.badge-online { background: #ecfdf5; color: #065f46; }
.badge-offline { background: #fef3c7; color: #92400e; }

.detail-price { text-align: right; font-size: 0.72rem; color: var(--color-text-secondary); line-height: 1.5; }
.detail-price strong { color: var(--color-text); font-weight: 600; }

/* ===== CTA / QR Section ===== */
.cta { padding: 6rem 0; }

.cta-inner {
  background: var(--color-white);
  border: 1px solid var(--color-border);
  border-radius: 20px;
  padding: 3rem;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 3rem;
  max-width: 600px;
  margin: 0 auto;
}

.cta-avatar {
  width: 72px; height: 72px; border-radius: 50%;
  object-fit: cover; flex-shrink: 0;
  background: var(--color-tag-bg);
}

.cta-center { text-align: center; }

.cta-center h2 {
  font-family: var(--font-serif);
  font-size: 1.5rem; font-weight: 700;
  letter-spacing: -0.02em; margin-bottom: 0.3rem;
}
.cta-center p {
  font-size: 0.9rem; color: var(--color-text-secondary); margin-bottom: 1.25rem;
}

.cta-qrcode {
  width: 160px; height: 160px;
  border-radius: var(--radius);
  border: 1px solid var(--color-border);
}

/* ===== Footer ===== */
.footer {
  padding: 2.5rem 0; border-top: 1px solid var(--color-border); text-align: center;
}
.footer p { font-size: 0.85rem; color: var(--color-text-secondary); }

/* ===== Animations ===== */
.fade-in {
  opacity: 0; transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}
.fade-in.visible { opacity: 1; transform: translateY(0); }

/* ===== Responsive ===== */
@media (max-width: 900px) {
  .mentors-grid { grid-template-columns: repeat(3, 1fr); }
}

@media (max-width: 768px) {
  .nav-links { display: none; }
  .nav-toggle { display: flex; }
  .nav-inner { padding: 0 1.25rem; }
  .container { padding: 0 1.25rem; }

  .hero { padding: 7rem 1.25rem 4rem; }
  .hero-title { font-size: 1.75rem; }

  .flow { flex-direction: column; gap: 1rem; align-items: center; }
  .flow-step { max-width: 280px; }
  .flow-step:not(:last-child)::after {
    content: "↓"; position: static; transform: none;
    display: block; text-align: center; margin: 0.25rem 0; font-size: 1rem;
  }

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

  .mentors-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 0.75rem;
  }

  .cta-inner {
    flex-direction: column; gap: 1.5rem; padding: 2rem 1.5rem;
  }
}

@media (max-width: 480px) {
  .hero-title { font-size: 1.5rem; }
  .mentors-grid { grid-template-columns: repeat(2, 1fr); gap: 0.6rem; }
  .mentor-summary { padding: 1.25rem 0.75rem 1rem; }
  .mentor-avatar { width: 60px; height: 60px; }
  .mentor-avatar-letter { font-size: 1.35rem; }
  .mentor-name { font-size: 0.92rem; }
  .cta-inner { padding: 1.5rem 1rem; }
  .cta-qrcode { width: 140px; height: 140px; }
}