/* ========================================
   IST - InterSolution Technology
   Modern Minimal Design System
   ======================================== */

/* CSS Variables */
:root {
  /* Colors */
  --primary: #0a0a0a;
  --primary-light: #1a1a1a;
  --secondary: #ffffff;
  --accent: #2563eb;
  --accent-light: #3b82f6;
  --accent-dark: #1d4ed8;
  --gray-50: #fafafa;
  --gray-100: #f5f5f5;
  --gray-200: #e5e5e5;
  --gray-300: #d4d4d4;
  --gray-400: #a3a3a3;
  --gray-500: #737373;
  --gray-600: #525252;
  --gray-700: #404040;
  --gray-800: #262626;
  --gray-900: #171717;

  /* Typography */
  --font-sans: 'Pretendard', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-display: 'Pretendard', sans-serif;

  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;
  --space-3xl: 4rem;
  --space-4xl: 6rem;
  --space-5xl: 8rem;

  /* Container */
  --container-max: 1280px;
  --container-padding: 1.5rem;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 300ms ease;
  --transition-slow: 500ms ease;

  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
  --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);

  /* Border Radius */
  --radius-sm: 0.25rem;
  --radius-md: 0.5rem;
  --radius-lg: 1rem;
  --radius-xl: 1.5rem;
  --radius-full: 9999px;
}

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

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

body {
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.6;
  color: var(--gray-700);
  background-color: var(--secondary);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-display);
  font-weight: 700;
  color: var(--primary);
  line-height: 1.2;
  letter-spacing: -0.02em;
}

h1 { font-size: clamp(2.5rem, 5vw, 4rem); }
h2 { font-size: clamp(2rem, 4vw, 3rem); }
h3 { font-size: clamp(1.5rem, 3vw, 2rem); }
h4 { font-size: clamp(1.25rem, 2vw, 1.5rem); }
h5 { font-size: 1.125rem; }
h6 { font-size: 1rem; }

p {
  margin-bottom: var(--space-md);
  color: var(--gray-600);
}

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

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

ul, ol {
  list-style: none;
}

/* Container */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--container-padding);
}

/* ========================================
   Header / Navigation
   ======================================== */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid transparent;
  transition: all var(--transition-base);
}

.header.scrolled {
  border-bottom-color: var(--gray-200);
  box-shadow: var(--shadow-sm);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 80px;
}

.logo {
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--primary);
  letter-spacing: -0.03em;
}

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

.nav {
  display: flex;
  align-items: center;
  gap: var(--space-xl);
}

.nav-link {
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--gray-600);
  position: relative;
  padding: var(--space-sm) 0;
}

.nav-link::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--accent);
  transition: width var(--transition-base);
}

.nav-link:hover,
.nav-link.active {
  color: var(--primary);
}

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

/* Mobile Menu Toggle */
.menu-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  padding: 10px;
  background: none;
  border: none;
  cursor: pointer;
}

.menu-toggle span {
  width: 24px;
  height: 2px;
  background: var(--primary);
  transition: all var(--transition-fast);
}

/* ========================================
   Hero Section
   ======================================== */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding-top: 80px;
  position: relative;
  overflow: hidden;
}

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

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-sm) var(--space-md);
  background: var(--gray-100);
  border-radius: var(--radius-full);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--gray-600);
  margin-bottom: var(--space-xl);
}

.hero-badge::before {
  content: '';
  width: 8px;
  height: 8px;
  background: var(--accent);
  border-radius: 50%;
  animation: pulse 2s infinite;
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.5; }
}

.hero-title {
  margin-bottom: var(--space-lg);
}

.hero-title .highlight {
  color: var(--accent);
}

.hero-description {
  font-size: 1.25rem;
  color: var(--gray-500);
  max-width: 600px;
  margin-bottom: var(--space-2xl);
}

.hero-cta {
  display: flex;
  gap: var(--space-md);
  flex-wrap: wrap;
}

/* Floating Elements */
.hero-visual {
  position: absolute;
  right: -5%;
  top: 50%;
  transform: translateY(-50%);
  width: 50%;
  height: 80%;
  background: linear-gradient(135deg, var(--accent) 0%, var(--accent-dark) 100%);
  border-radius: var(--radius-xl);
  opacity: 0.1;
}

/* ========================================
   Buttons
   ======================================== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  padding: var(--space-md) var(--space-xl);
  font-family: var(--font-sans);
  font-size: 0.9375rem;
  font-weight: 600;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-fast);
}

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

.btn-primary:hover {
  background: var(--primary-light);
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.btn-secondary {
  background: transparent;
  color: var(--primary);
  border: 1px solid var(--gray-300);
}

.btn-secondary:hover {
  border-color: var(--primary);
  background: var(--gray-50);
}

.btn-accent {
  background: var(--accent);
  color: var(--secondary);
}

.btn-accent:hover {
  background: var(--accent-dark);
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.btn-lg {
  padding: var(--space-lg) var(--space-2xl);
  font-size: 1rem;
}

/* ========================================
   Sections
   ======================================== */
.section {
  padding: var(--space-5xl) 0;
}

.section-header {
  text-align: center;
  max-width: 700px;
  margin: 0 auto var(--space-4xl);
}

.section-label {
  display: inline-block;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: var(--space-md);
}

.section-title {
  margin-bottom: var(--space-lg);
}

.section-description {
  font-size: 1.125rem;
  color: var(--gray-500);
}

/* Background Variations */
.section-gray {
  background: var(--gray-50);
}

.section-dark {
  background: var(--primary);
}

.section-dark .section-label {
  color: var(--accent-light);
}

.section-dark .section-title {
  color: var(--secondary);
}

.section-dark .section-description {
  color: var(--gray-400);
}

/* ========================================
   Cards
   ======================================== */
.card {
  background: var(--secondary);
  border-radius: var(--radius-lg);
  padding: var(--space-2xl);
  transition: all var(--transition-base);
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-xl);
}

.card-icon {
  width: 56px;
  height: 56px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--gray-100);
  border-radius: var(--radius-md);
  margin-bottom: var(--space-lg);
  font-size: 1.5rem;
}

.card-title {
  font-size: 1.25rem;
  margin-bottom: var(--space-md);
}

.card-description {
  color: var(--gray-500);
  margin-bottom: 0;
}

/* Card Grid */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: var(--space-xl);
}

/* ========================================
   Stats
   ======================================== */
.stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--space-2xl);
}

.stat {
  text-align: center;
}

.stat-number {
  font-size: clamp(2.5rem, 5vw, 3.5rem);
  font-weight: 800;
  color: var(--primary);
  line-height: 1;
  margin-bottom: var(--space-sm);
}

.stat-number span {
  color: var(--accent);
}

.stat-label {
  font-size: 0.9375rem;
  color: var(--gray-500);
  font-weight: 500;
}

/* ========================================
   Feature List
   ======================================== */
.feature-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-lg);
}

.feature-item {
  display: flex;
  align-items: flex-start;
  gap: var(--space-md);
}

.feature-check {
  width: 24px;
  height: 24px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--accent);
  color: var(--secondary);
  border-radius: 50%;
  font-size: 0.75rem;
  flex-shrink: 0;
  margin-top: 2px;
}

.feature-text {
  color: var(--gray-600);
}

/* ========================================
   Timeline
   ======================================== */
.timeline {
  position: relative;
  padding-left: var(--space-2xl);
}

.timeline::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: 2px;
  background: var(--gray-200);
}

.timeline-item {
  position: relative;
  padding-bottom: var(--space-2xl);
}

.timeline-item::before {
  content: '';
  position: absolute;
  left: calc(-1 * var(--space-2xl) - 5px);
  top: 6px;
  width: 12px;
  height: 12px;
  background: var(--accent);
  border-radius: 50%;
}

.timeline-year {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--accent);
  margin-bottom: var(--space-xs);
}

.timeline-title {
  font-size: 1.125rem;
  font-weight: 600;
  color: var(--primary);
  margin-bottom: var(--space-xs);
}

.timeline-description {
  color: var(--gray-500);
  margin-bottom: 0;
}

/* ========================================
   Clients / Logos
   ======================================== */
.client-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: var(--space-xl);
  align-items: center;
}

.client-logo {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-lg);
  background: var(--gray-50);
  border-radius: var(--radius-md);
  font-weight: 600;
  color: var(--gray-400);
  transition: all var(--transition-base);
}

.client-logo:hover {
  background: var(--secondary);
  color: var(--gray-600);
  box-shadow: var(--shadow-md);
}

/* ========================================
   Contact Form
   ======================================== */
.form-group {
  margin-bottom: var(--space-lg);
}

.form-label {
  display: block;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--gray-700);
  margin-bottom: var(--space-sm);
}

.form-input,
.form-textarea {
  width: 100%;
  padding: var(--space-md);
  font-family: var(--font-sans);
  font-size: 1rem;
  color: var(--gray-700);
  background: var(--gray-50);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
}

.form-input:focus,
.form-textarea:focus {
  outline: none;
  border-color: var(--accent);
  background: var(--secondary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

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

/* ========================================
   Footer
   ======================================== */
.footer {
  background: var(--primary);
  color: var(--gray-400);
  padding: var(--space-4xl) 0 var(--space-2xl);
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: var(--space-3xl);
  margin-bottom: var(--space-3xl);
}

.footer-brand {
  max-width: 300px;
}

.footer-logo {
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--secondary);
  margin-bottom: var(--space-md);
}

.footer-logo span {
  color: var(--accent-light);
}

.footer-description {
  color: var(--gray-400);
  margin-bottom: var(--space-lg);
}

.footer-title {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--secondary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: var(--space-lg);
}

.footer-links {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.footer-link {
  color: var(--gray-400);
  font-size: 0.9375rem;
  transition: color var(--transition-fast);
}

.footer-link:hover {
  color: var(--secondary);
}

.footer-bottom {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-top: var(--space-2xl);
  border-top: 1px solid var(--gray-800);
}

.footer-copyright {
  font-size: 0.875rem;
}

.footer-social {
  display: flex;
  gap: var(--space-md);
}

.social-link {
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--gray-800);
  border-radius: var(--radius-md);
  color: var(--gray-400);
  transition: all var(--transition-fast);
}

.social-link:hover {
  background: var(--accent);
  color: var(--secondary);
}

/* ========================================
   Page Header
   ======================================== */
.page-header {
  padding: calc(80px + var(--space-4xl)) 0 var(--space-4xl);
  background: var(--gray-50);
  text-align: center;
}

.page-title {
  margin-bottom: var(--space-md);
}

.page-description {
  font-size: 1.125rem;
  color: var(--gray-500);
  max-width: 600px;
  margin: 0 auto;
}

/* Breadcrumb */
.breadcrumb {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  font-size: 0.875rem;
  color: var(--gray-500);
  margin-bottom: var(--space-lg);
}

.breadcrumb a {
  color: var(--gray-500);
}

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

.breadcrumb span {
  color: var(--gray-400);
}

/* ========================================
   Tabs
   ======================================== */
.tabs {
  display: flex;
  gap: var(--space-sm);
  border-bottom: 1px solid var(--gray-200);
  margin-bottom: var(--space-2xl);
  overflow-x: auto;
}

.tab {
  padding: var(--space-md) var(--space-lg);
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--gray-500);
  background: none;
  border: none;
  cursor: pointer;
  position: relative;
  white-space: nowrap;
  transition: color var(--transition-fast);
}

.tab::after {
  content: '';
  position: absolute;
  bottom: -1px;
  left: 0;
  right: 0;
  height: 2px;
  background: var(--accent);
  transform: scaleX(0);
  transition: transform var(--transition-fast);
}

.tab:hover {
  color: var(--primary);
}

.tab.active {
  color: var(--accent);
}

.tab.active::after {
  transform: scaleX(1);
}

/* ========================================
   Project Cards
   ======================================== */
.project-card {
  background: var(--secondary);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  transition: all var(--transition-base);
}

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

.project-category {
  display: inline-block;
  padding: var(--space-xs) var(--space-sm);
  background: var(--gray-100);
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--gray-600);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: var(--space-md);
}

.project-title {
  font-size: 1.125rem;
  margin-bottom: var(--space-sm);
}

.project-client {
  font-size: 0.875rem;
  color: var(--gray-500);
}

/* ========================================
   CEO Section
   ======================================== */
.ceo-section {
  display: grid;
  grid-template-columns: 1fr 1.5fr;
  gap: var(--space-4xl);
  align-items: start;
}

.ceo-image {
  position: relative;
}

.ceo-image-placeholder {
  aspect-ratio: 3/4;
  background: linear-gradient(135deg, var(--gray-200) 0%, var(--gray-100) 100%);
  border-radius: var(--radius-xl);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 4rem;
  color: var(--gray-400);
}

.ceo-content h2 {
  margin-bottom: var(--space-sm);
}

.ceo-position {
  font-size: 1.125rem;
  color: var(--accent);
  font-weight: 500;
  margin-bottom: var(--space-xl);
}

.ceo-message {
  font-size: 1.125rem;
  line-height: 1.8;
  color: var(--gray-600);
  margin-bottom: var(--space-2xl);
}

.ceo-signature {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--primary);
}

/* ========================================
   Contact Info
   ======================================== */
.contact-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-4xl);
}

.contact-info-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-xl);
}

.contact-info-item {
  display: flex;
  gap: var(--space-md);
}

.contact-info-icon {
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--gray-100);
  border-radius: var(--radius-md);
  font-size: 1.25rem;
  flex-shrink: 0;
}

.contact-info-label {
  font-size: 0.875rem;
  color: var(--gray-500);
  margin-bottom: var(--space-xs);
}

.contact-info-value {
  font-weight: 600;
  color: var(--primary);
}

/* Map Placeholder */
.map-container {
  height: 400px;
  background: var(--gray-100);
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--gray-400);
}

/* ========================================
   Animations
   ======================================== */
.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: all var(--transition-slow);
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

.slide-in-left {
  opacity: 0;
  transform: translateX(-30px);
  transition: all var(--transition-slow);
}

.slide-in-left.visible {
  opacity: 1;
  transform: translateX(0);
}

.slide-in-right {
  opacity: 0;
  transform: translateX(30px);
  transition: all var(--transition-slow);
}

.slide-in-right.visible {
  opacity: 1;
  transform: translateX(0);
}

/* Stagger animation delays */
.stagger > *:nth-child(1) { transition-delay: 0ms; }
.stagger > *:nth-child(2) { transition-delay: 100ms; }
.stagger > *:nth-child(3) { transition-delay: 200ms; }
.stagger > *:nth-child(4) { transition-delay: 300ms; }
.stagger > *:nth-child(5) { transition-delay: 400ms; }
.stagger > *:nth-child(6) { transition-delay: 500ms; }

/* ========================================
   Utilities
   ======================================== */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.mt-0 { margin-top: 0; }
.mt-1 { margin-top: var(--space-md); }
.mt-2 { margin-top: var(--space-xl); }
.mt-3 { margin-top: var(--space-2xl); }
.mt-4 { margin-top: var(--space-3xl); }

.mb-0 { margin-bottom: 0; }
.mb-1 { margin-bottom: var(--space-md); }
.mb-2 { margin-bottom: var(--space-xl); }
.mb-3 { margin-bottom: var(--space-2xl); }
.mb-4 { margin-bottom: var(--space-3xl); }

.grid-2 {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-2xl);
}

.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-2xl);
}

/* ========================================
   Responsive
   ======================================== */
@media (max-width: 1024px) {
  .footer-grid {
    grid-template-columns: 1fr 1fr;
  }

  .ceo-section {
    grid-template-columns: 1fr;
  }

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

  .grid-3 {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 768px) {
  :root {
    --container-padding: 1rem;
  }

  .header-inner {
    height: 70px;
  }

  .nav {
    position: fixed;
    top: 70px;
    left: 0;
    right: 0;
    background: var(--secondary);
    flex-direction: column;
    padding: var(--space-xl);
    gap: var(--space-lg);
    border-bottom: 1px solid var(--gray-200);
    transform: translateY(-100%);
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-base);
  }

  .nav.active {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }

  .menu-toggle {
    display: flex;
  }

  .menu-toggle.active span:nth-child(1) {
    transform: translateY(7px) rotate(45deg);
  }

  .menu-toggle.active span:nth-child(2) {
    opacity: 0;
  }

  .menu-toggle.active span:nth-child(3) {
    transform: translateY(-7px) rotate(-45deg);
  }

  .hero {
    min-height: auto;
    padding: calc(70px + var(--space-3xl)) 0 var(--space-3xl);
  }

  .hero-visual {
    display: none;
  }

  .hero-cta {
    flex-direction: column;
  }

  .section {
    padding: var(--space-3xl) 0;
  }

  .footer-grid {
    grid-template-columns: 1fr;
    gap: var(--space-2xl);
  }

  .footer-bottom {
    flex-direction: column;
    gap: var(--space-lg);
    text-align: center;
  }

  .grid-2,
  .grid-3 {
    grid-template-columns: 1fr;
  }

  .stats {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 480px) {
  .stats {
    grid-template-columns: 1fr;
  }

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

  .client-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}