/* Modern CSS Reset & Variables */
:root {
  /* Color Palette - Enterprise Blue & Sophisticated Grays */
  --primary-color: #0f172a; /* Deep Navy */
  --primary-light: #334155; /* Slate 700 */
  --primary-dark: #020617; /* Slate 950 */
  
  --accent-color: #3b82f6; /* Vibrant Blue */
  --accent-hover: #2563eb; /* Darker Blue */
  --accent-purple: #8b5cf6;
  --accent-green: #10b981;
  --accent-red: #ef4444;

  --text-primary: #1e293b; /* Slate 800 */
  --text-secondary: #64748b; /* Slate 500 */
  --text-light: #94a3b8; /* Slate 400 */
  --text-white: #ffffff;

  --bg-primary: #ffffff;
  --bg-secondary: #f8fafc; /* Slate 50 */
  --bg-accent: #f1f5f9; /* Slate 100 */
  --bg-dark: #0f172a;

  --border-color: #e2e8f0; /* Slate 200 */
  
  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-md: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --shadow-lg: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
  --shadow-glow: 0 0 20px rgba(59, 130, 246, 0.5);

  /* Transitions */
  --transition-base: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

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

body {
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  line-height: 1.6;
  color: var(--text-primary);
  background-color: var(--bg-primary);
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-family: "Poppins", sans-serif;
  line-height: 1.2;
  color: var(--primary-color);
}

a {
  text-decoration: none;
  color: inherit;
  transition: var(--transition-base);
}

ul {
  list-style: none;
}

/* Header & Navigation */
.header {
  position: fixed;
  top: 0;
  width: 100%;
  background: rgba(255, 255, 255, 0.8);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid rgba(226, 232, 240, 0.6);
  z-index: 1000;
  transition: var(--transition-base);
}

.header.scrolled {
  background: rgba(255, 255, 255, 0.95);
  box-shadow: var(--shadow-sm);
}

.nav {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 2rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 80px;
}

.logo {
  font-size: 1.75rem;
  font-weight: 800;
  color: var(--primary-color);
  letter-spacing: -0.02em;
}

.nav-links {
  display: flex;
  gap: 2.5rem;
  align-items: center;
}

.nav-link {
  color: var(--text-secondary);
  font-weight: 500;
  font-size: 0.95rem;
  position: relative;
}

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

.nav-link::after {
  content: "";
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--accent-color);
  transition: width 0.3s ease;
  border-radius: 2px;
}

.nav-link:hover::after {
  width: 100%;
}

/* Language Switcher */
.lang-switch {
  position: relative;
}

.lang-selector {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.5rem 1rem;
  background: transparent;
  border: 1px solid var(--border-color);
  border-radius: 9999px; /* Pill shape */
  color: var(--text-secondary);
  cursor: pointer;
  transition: var(--transition-base);
  font-weight: 500;
  font-size: 0.9rem;
}

.lang-selector:hover {
  border-color: var(--accent-color);
  color: var(--accent-color);
  background: var(--bg-secondary);
}

.lang-dropdown {
  position: absolute;
  top: calc(100% + 0.75rem);
  right: 0;
  background: white;
  border: 1px solid var(--border-color);
  border-radius: 12px;
  box-shadow: var(--shadow-lg);
  min-width: 140px;
  opacity: 0;
  visibility: hidden;
  transform: translateY(-10px);
  transition: var(--transition-base);
  overflow: hidden;
}

.lang-switch.active .lang-dropdown {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.lang-option {
  padding: 0.75rem 1.25rem;
  display: block;
  color: var(--text-secondary);
  font-weight: 500;
  font-size: 0.9rem;
}

.lang-option:hover {
  background: var(--bg-secondary);
  color: var(--accent-color);
}

.lang-option.active {
  background: var(--bg-accent);
  color: var(--accent-color);
  font-weight: 600;
}

[lang]:not([lang="ko"]) .ko-only,
[lang]:not([lang="en"]) .en-only {
  display: none !important;
}

/* Hero Section */
.hero {
  padding: 180px 0 120px;
  background: radial-gradient(circle at top right, #1e293b, #0f172a);
  position: relative;
  overflow: hidden;
  color: white;
}

.hero::before {
  content: "";
  position: absolute;
  top: -50%;
  right: -20%;
  width: 80%;
  height: 200%;
  background: radial-gradient(circle, rgba(59, 130, 246, 0.15) 0%, transparent 60%);
  transform: rotate(-15deg);
  pointer-events: none;
}

.hero-content {
  max-width: 1000px;
  margin: 0 auto;
  padding: 0 2rem;
  text-align: center;
  position: relative;
  z-index: 1;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: rgba(255, 255, 255, 0.1);
  border: 1px solid rgba(255, 255, 255, 0.2);
  color: #e2e8f0;
  padding: 0.5rem 1.25rem;
  border-radius: 9999px;
  font-size: 0.875rem;
  font-weight: 600;
  margin-bottom: 2.5rem;
  backdrop-filter: blur(4px);
}

.hero h1 {
  font-size: 4.5rem;
  font-weight: 800;
  margin-bottom: 1.5rem;
  color: white;
  line-height: 1.1;
  letter-spacing: -0.03em;
}

.hero h1 .highlight {
  background: linear-gradient(135deg, #60a5fa, #a78bfa);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero .subtitle {
  font-size: 1.35rem;
  color: #cbd5e1;
  margin-bottom: 3.5rem;
  font-weight: 400;
  max-width: 800px;
  margin-left: auto;
  margin-right: auto;
}

.hero-cta {
  display: flex;
  gap: 1rem;
  justify-content: center;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.75rem;
  padding: 1rem 2.5rem;
  border-radius: 9999px;
  font-weight: 600;
  font-size: 1rem;
  transition: var(--transition-base);
  cursor: pointer;
  border: none;
}

.btn-primary {
  background: var(--accent-color);
  color: white;
  box-shadow: 0 4px 6px -1px rgba(59, 130, 246, 0.3);
}

.btn-primary:hover {
  background: var(--accent-hover);
  transform: translateY(-2px);
  box-shadow: 0 10px 15px -3px rgba(59, 130, 246, 0.4);
}

.btn-outline {
  background: transparent;
  color: white;
  border: 1px solid rgba(255, 255, 255, 0.3);
}

.btn-outline:hover {
  background: rgba(255, 255, 255, 0.1);
  border-color: white;
  transform: translateY(-2px);
}

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

.btn-white:hover {
  background: var(--bg-secondary);
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

/* Sections */
.section {
  padding: 100px 0;
}

.main {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 2rem;
}

.section-title {
  font-size: 2.5rem;
  font-weight: 700;
  text-align: center;
  margin-bottom: 1rem;
  color: var(--primary-color);
  letter-spacing: -0.02em;
}

.section-subtitle {
  font-size: 1.125rem;
  color: var(--text-secondary);
  text-align: center;
  margin-bottom: 5rem;
  max-width: 700px;
  margin-left: auto;
  margin-right: auto;
}

/* Cards & Grids */
.grid {
  display: grid;
  gap: 2.5rem;
}

.grid-3 {
  grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
}

.grid-4 {
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

.card {
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 24px;
  padding: 2.5rem;
  transition: var(--transition-base);
  height: 100%;
  display: flex;
  flex-direction: column;
}

.card:hover {
  transform: translateY(-8px);
  box-shadow: var(--shadow-lg);
  border-color: var(--accent-color);
}

.card-icon {
  width: 64px;
  height: 64px;
  background: var(--bg-secondary);
  border-radius: 16px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 1.5rem;
  color: var(--accent-color);
  font-size: 1.75rem;
  transition: var(--transition-base);
}

.card:hover .card-icon {
  background: var(--accent-color);
  color: white;
  transform: scale(1.1) rotate(-5deg);
}

.card h3 {
  font-size: 1.35rem;
  font-weight: 700;
  margin-bottom: 1rem;
  color: var(--primary-color);
}

.card p {
  color: var(--text-secondary);
  line-height: 1.7;
  flex-grow: 1;
}

/* Comparison Section */
.comparison-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
  gap: 3rem;
  margin-bottom: 3rem;
}

.comparison-card {
  border-radius: 24px;
  padding: 3rem;
  position: relative;
  overflow: hidden;
}

.comparison-card.problem {
  background: #fff1f2;
  border: 1px solid #fecdd3;
}

.comparison-card.solution {
  background: #f0fdf4;
  border: 1px solid #bbf7d0;
  box-shadow: var(--shadow-md);
}

.comparison-header {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-bottom: 2rem;
}

.comparison-icon {
  font-size: 2rem;
}

.problem .comparison-icon { color: var(--accent-red); }
.solution .comparison-icon { color: var(--accent-green); }

.comparison-list li {
  padding: 1rem 0;
  padding-left: 2.5rem;
  position: relative;
  color: var(--text-primary);
  border-bottom: 1px solid rgba(0,0,0,0.05);
}

.comparison-list li:last-child { border-bottom: none; }

.comparison-list li::before {
  position: absolute;
  left: 0;
  top: 1.1rem;
  font-family: "Font Awesome 6 Free";
  font-weight: 900;
}

.problem .comparison-list li::before {
  content: "\f00d";
  color: var(--accent-red);
}

.solution .comparison-list li::before {
  content: "\f00c";
  color: var(--accent-green);
}

/* Scalability Steps */
.scalability-steps {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 2rem;
  counter-reset: step;
}

.step-card {
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 24px;
  padding: 3rem 2rem;
  text-align: center;
  position: relative;
  transition: var(--transition-base);
}

.step-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-lg);
}

.step-number {
  width: 60px;
  height: 60px;
  background: var(--bg-secondary);
  color: var(--primary-color);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  font-weight: 800;
  margin: 0 auto 2rem;
  border: 2px solid var(--border-color);
  transition: var(--transition-base);
}

.step-card:hover .step-number {
  background: var(--accent-color);
  color: white;
  border-color: var(--accent-color);
}

.step-card .step-title {
  color: var(--accent-color);
  font-weight: 600;
  margin-bottom: 1rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-size: 0.875rem;
}

/* Architecture Diagram */
.arch-diagram {
  background: var(--bg-secondary);
  border-radius: 16px;
  padding: 2rem;
  margin-bottom: 2rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
}

.arch-node {
  background: white;
  padding: 0.75rem 1.5rem;
  border-radius: 12px;
  font-weight: 600;
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--border-color);
  min-width: 120px;
}

.arch-arrow {
  color: var(--text-light);
}

/* Pricing */
.pricing-container {
  max-width: 800px;
  margin: 0 auto;
  background: white;
  border-radius: 32px;
  padding: 4rem;
  box-shadow: var(--shadow-xl);
  border: 1px solid var(--border-color);
}

.pricing-list li {
  padding: 1.25rem 0;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  gap: 1rem;
  font-size: 1.1rem;
}

.pricing-list li i {
  color: var(--accent-color);
}

/* CTA Section */
.cta-section {
  background: var(--primary-color);
  padding: 120px 0;
  text-align: center;
  color: white;
  position: relative;
  overflow: hidden;
}

.cta-section::after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: url("data:image/svg+xml,%3Csvg width='60' height='60' viewBox='0 0 60 60' xmlns='http://www.w3.org/2000/svg'%3E%3Cg fill='none' fill-rule='evenodd'%3E%3Cg fill='%23ffffff' fill-opacity='0.05'%3E%3Cpath d='M36 34v-4h-2v4h-4v2h4v4h2v-4h4v-2h-4zm0-30V0h-2v4h-4v2h4v4h2V6h4V4h-4zM6 34v-4H4v4H0v2h4v4h2v-4h4v-2H6zM6 4V0H4v4H0v2h4v4h2V6h4V4H6z'/%3E%3C/g%3E%3C/g%3E%3C/svg%3E");
}

.cta-content {
  position: relative;
  z-index: 1;
  max-width: 800px;
  margin: 0 auto;
  padding: 0 2rem;
}

.cta-section h2 {
  color: white;
  font-size: 3rem;
  margin-bottom: 1.5rem;
}

.cta-section p {
  font-size: 1.25rem;
  color: #cbd5e1;
  margin-bottom: 3rem;
}

/* Footer */
.footer {
  background: var(--primary-dark);
  color: var(--text-light);
  padding: 60px 0;
  text-align: center;
  border-top: 1px solid rgba(255,255,255,0.1);
}

/* Animations */
.animate-on-scroll {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.8s ease-out, transform 0.8s ease-out;
}

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

/* Responsive */
@media (max-width: 1024px) {
  .hero h1 { font-size: 3.5rem; }
}

@media (max-width: 768px) {
  .nav { height: auto; padding: 1rem; }
  .nav > div { flex-direction: column; gap: 1rem !important; width: 100%; }
  .nav-links { gap: 1.5rem; flex-wrap: wrap; justify-content: center; }
  
  .hero { padding: 140px 0 80px; }
  .hero h1 { font-size: 2.5rem; }
  .hero-cta { flex-direction: column; }
  .btn { width: 100%; justify-content: center; }
  
  .grid-3, .grid-4, .comparison-grid, .scalability-steps { grid-template-columns: 1fr; }
  
  .section { padding: 60px 0; }
  .section-title { font-size: 2rem; }
  
  .cta-section h2 { font-size: 2.25rem; }
}