/* 
  OSCAT Website Stylesheet
  Design System for Automation Technology Community
  Uses system-preference-aware dark mode & premium interactive states.
*/

/* Google Fonts Import */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=Outfit:wght@400;500;600;700;800&display=swap');

:root {
  --font-heading: 'Outfit', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-body: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  
  /* Color Palette - Premium Technical Blue */
  --bg-primary: #f8fafc;
  --bg-secondary: #ffffff;
  --bg-tertiary: #f1f5f9;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #64748b;
  --accent-color: #0284c7;
  --accent-hover: #0369a1;
  --accent-glow: rgba(2, 132, 199, 0.08);
  --border-color: #e2e8f0;
  
  --card-bg: rgba(255, 255, 255, 0.85);
  --card-border: rgba(226, 232, 240, 0.8);
  --card-shadow: 0 10px 30px -10px rgba(0, 0, 0, 0.04);
  --card-shadow-hover: 0 20px 40px -15px rgba(2, 132, 199, 0.12);
  
  /* Library Colors */
  --color-basic: #2563eb;
  --color-basic-glow: rgba(37, 99, 235, 0.06);
  --color-network: #0d9488;
  --color-network-glow: rgba(13, 148, 136, 0.06);
  --color-building: #d97706;
  --color-building-glow: rgba(217, 119, 6, 0.06);
  
  --transition-smooth: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-bounce: all 0.5s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg-primary: #090e1a;
    --bg-secondary: #0f172a;
    --bg-tertiary: #1e293b;
    --text-primary: #f8fafc;
    --text-secondary: #cbd5e1;
    --text-muted: #64748b;
    --accent-color: #38bdf8;
    --accent-hover: #7dd3fc;
    --accent-glow: rgba(56, 189, 248, 0.12);
    --border-color: #1e293b;
    
    --card-bg: rgba(15, 23, 42, 0.65);
    --card-border: rgba(30, 41, 59, 0.7);
    --card-shadow: 0 15px 35px -10px rgba(0, 0, 0, 0.3);
    --card-shadow-hover: 0 25px 50px -15px rgba(56, 189, 248, 0.18);
    
    --color-basic: #3b82f6;
    --color-basic-glow: rgba(59, 130, 246, 0.12);
    --color-network: #14b8a6;
    --color-network-glow: rgba(20, 184, 166, 0.12);
    --color-building: #f59e0b;
    --color-building-glow: rgba(245, 158, 11, 0.12);
  }
}

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

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

body {
  font-family: var(--font-body);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  overflow-x: hidden;
  transition: background-color 0.3s ease, color 0.3s ease;
  position: relative;
}

/* Language Selection Rules */
body.lang-de [lang="en"] {
  display: none !important;
}
body.lang-en [lang="de"] {
  display: none !important;
}

/* Navigation / Header Bar */
.header-bar {
  position: fixed;
  top: 1.5rem;
  left: 50%;
  transform: translateX(-50%);
  width: 90%;
  max-width: 1200px;
  background: var(--card-bg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--card-border);
  padding: 0.75rem 2rem;
  border-radius: 50px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  z-index: 1000;
  box-shadow: var(--card-shadow);
  transition: var(--transition-smooth);
}

.brand-container {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none;
}

.brand-logo-small {
  width: 36px;
  height: 36px;
  border-radius: 10px;
  object-fit: cover;
  background: white;
  padding: 2px;
  border: 1px solid var(--border-color);
  box-shadow: 0 4px 10px rgba(0, 0, 0, 0.05);
}

.brand-name {
  font-family: var(--font-heading);
  font-weight: 800;
  font-size: 1.35rem;
  letter-spacing: -0.5px;
  background: linear-gradient(135deg, var(--text-primary) 0%, var(--accent-color) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

/* Language Toggle Button Group */
.lang-toggle {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  padding: 0.25rem;
  border-radius: 30px;
  display: flex;
  gap: 0.25rem;
}

.lang-toggle-btn {
  background: transparent;
  border: none;
  color: var(--text-muted);
  font-family: var(--font-body);
  font-weight: 600;
  font-size: 0.85rem;
  padding: 0.5rem 1.25rem;
  border-radius: 20px;
  cursor: pointer;
  transition: var(--transition-smooth);
}

.lang-toggle-btn:hover {
  color: var(--text-primary);
}

.lang-toggle-btn.active {
  background: var(--bg-secondary);
  color: var(--accent-color);
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.08);
}

/* Hero Section */
.hero-section {
  position: relative;
  min-height: 95vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
  padding: 8rem 2rem 4rem 2rem;
  background-image: 
    radial-gradient(circle at 10% 20%, var(--accent-glow) 0%, transparent 45%),
    radial-gradient(circle at 90% 80%, rgba(13, 148, 136, 0.06) 0%, transparent 45%);
}

.bg-grid {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-image: radial-gradient(var(--border-color) 1.2px, transparent 1.2px);
  background-size: 36px 36px;
  opacity: 0.5;
  mask-image: radial-gradient(circle at 50% 50%, black 30%, transparent 95%);
  -webkit-mask-image: radial-gradient(circle at 50% 50%, black 30%, transparent 95%);
  z-index: 0;
  pointer-events: none;
}

.hero-logo-container {
  position: relative;
  margin-bottom: 2.5rem;
  display: inline-block;
  z-index: 1;
}

.hero-logo-container::before {
  content: '';
  position: absolute;
  top: -12px;
  left: -12px;
  right: -12px;
  bottom: -12px;
  background: linear-gradient(135deg, var(--accent-color), var(--color-network));
  border-radius: 40px;
  z-index: -1;
  filter: blur(24px);
  opacity: 0.25;
  animation: pulse 8s infinite alternate;
}

@keyframes pulse {
  0% { transform: scale(1); opacity: 0.25; filter: blur(24px); }
  100% { transform: scale(1.08); opacity: 0.45; filter: blur(36px); }
}

.hero-logo {
  width: 160px;
  height: 160px;
  object-fit: cover;
  border-radius: 32px;
  background: white;
  padding: 0.6rem;
  border: 1px solid var(--border-color);
  box-shadow: 0 20px 45px rgba(0, 0, 0, 0.08);
  transition: var(--transition-bounce);
}

.hero-logo:hover {
  transform: rotate(4deg) scale(1.05);
}

.hero-title {
  font-family: var(--font-heading);
  font-size: clamp(3rem, 9vw, 5.5rem);
  font-weight: 800;
  letter-spacing: -2.5px;
  line-height: 1.05;
  margin-bottom: 1.5rem;
  background: linear-gradient(135deg, var(--text-primary) 30%, var(--accent-color) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  z-index: 1;
}

.hero-subtitle {
  font-size: clamp(1.15rem, 3.5vw, 1.6rem);
  color: var(--text-secondary);
  max-width: 850px;
  margin-bottom: 3.5rem;
  font-weight: 400;
  z-index: 1;
  line-height: 1.5;
}

.hero-cta {
  display: flex;
  gap: 1.25rem;
  flex-wrap: wrap;
  justify-content: center;
  z-index: 1;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0.95rem 2.25rem;
  border-radius: 35px;
  font-family: var(--font-body);
  font-weight: 600;
  text-decoration: none;
  font-size: 1.05rem;
  transition: var(--transition-smooth);
  cursor: pointer;
}

.btn-primary {
  background: var(--accent-color);
  color: white;
  border: none;
  box-shadow: 0 10px 25px -5px rgba(2, 132, 199, 0.45);
}

.btn-primary:hover {
  background: var(--accent-hover);
  transform: translateY(-2px);
  box-shadow: 0 15px 35px -5px rgba(2, 132, 199, 0.65);
}

.btn-secondary {
  background: var(--bg-secondary);
  color: var(--text-primary);
  border: 1px solid var(--border-color);
  box-shadow: var(--card-shadow);
}

.btn-secondary:hover {
  background: var(--bg-tertiary);
  transform: translateY(-2px);
  box-shadow: 0 15px 30px -10px rgba(0, 0, 0, 0.1);
}

/* Container */
.container {
  width: 90%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 6rem 0;
}

/* Section Header */
.section-header {
  text-align: center;
  margin-bottom: 4.5rem;
}

.section-label {
  font-size: 0.875rem;
  text-transform: uppercase;
  letter-spacing: 3px;
  color: var(--accent-color);
  font-weight: 700;
  margin-bottom: 0.75rem;
  display: block;
}

.section-title {
  font-family: var(--font-heading);
  font-size: clamp(2.25rem, 6vw, 3.25rem);
  font-weight: 800;
  letter-spacing: -1.2px;
}

/* Library Cards Grid */
.cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
  gap: 2.25rem;
  margin-bottom: 2rem;
}

/* Library Card Design */
.lib-card {
  background: var(--card-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--card-border);
  border-radius: 28px;
  padding: 3rem 2.5rem;
  box-shadow: var(--card-shadow);
  transition: var(--transition-smooth);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  position: relative;
  overflow: hidden;
}

.lib-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 6px;
  background: var(--card-accent);
}

.lib-card:hover {
  transform: translateY(-10px);
  box-shadow: var(--card-shadow-hover);
  border-color: var(--card-accent-alpha);
}

.lib-card.basic {
  --card-accent: var(--color-basic);
  --card-accent-alpha: rgba(37, 99, 235, 0.4);
  background-image: radial-gradient(circle at 100% 100%, var(--color-basic-glow) 0%, transparent 60%);
}

.lib-card.network {
  --card-accent: var(--color-network);
  --card-accent-alpha: rgba(13, 148, 136, 0.4);
  background-image: radial-gradient(circle at 100% 100%, var(--color-network-glow) 0%, transparent 60%);
}

.lib-card.building {
  --card-accent: var(--color-building);
  --card-accent-alpha: rgba(217, 119, 6, 0.4);
  background-image: radial-gradient(circle at 100% 100%, var(--color-building-glow) 0%, transparent 60%);
}

.lib-header {
  margin-bottom: 2rem;
}

.lib-icon-wrapper {
  width: 64px;
  height: 64px;
  border-radius: 18px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg-tertiary);
  color: var(--card-accent);
  margin-bottom: 1.75rem;
  font-size: 1.85rem;
  transition: var(--transition-bounce);
  border: 1px solid var(--border-color);
}

.lib-card:hover .lib-icon-wrapper {
  transform: scale(1.1) rotate(6deg);
  background: var(--card-accent);
  color: white;
}

.lib-title {
  font-family: var(--font-heading);
  font-size: 1.85rem;
  font-weight: 700;
  margin-bottom: 0.85rem;
  letter-spacing: -0.6px;
}

.lib-desc {
  color: var(--text-secondary);
  font-size: 1.05rem;
  line-height: 1.65;
  margin-bottom: 2rem;
  flex-grow: 1;
}

.lib-link {
  display: inline-flex;
  align-items: center;
  gap: 0.55rem;
  color: var(--card-accent);
  text-decoration: none;
  font-weight: 700;
  transition: var(--transition-smooth);
}

.lib-link svg {
  transition: transform 0.3s ease;
}

.lib-link:hover {
  opacity: 0.95;
}

.lib-link:hover svg {
  transform: translateX(6px);
}

/* Feature grid */
.features-container {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 2rem;
  margin: 5rem 0 2rem 0;
}

.feature-item {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  padding: 2.25rem;
  border-radius: 24px;
  transition: var(--transition-smooth);
  box-shadow: var(--card-shadow);
}

.feature-item:hover {
  transform: translateY(-5px);
  border-color: var(--accent-color);
  box-shadow: 0 15px 30px rgba(0, 0, 0, 0.03);
}

.feature-icon-wrapper {
  width: 52px;
  height: 52px;
  border-radius: 14px;
  background: var(--accent-glow);
  color: var(--accent-color);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 1.5rem;
  border: 1px solid rgba(2, 132, 199, 0.1);
}

.feature-title {
  font-family: var(--font-heading);
  font-size: 1.3rem;
  font-weight: 700;
  margin-bottom: 0.6rem;
}

.feature-desc {
  color: var(--text-secondary);
  font-size: 0.95rem;
  line-height: 1.55;
}

/* Contributing Box Layout */
.contributing-box {
  background: var(--card-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--card-border);
  border-radius: 32px;
  padding: 4rem;
  box-shadow: var(--card-shadow);
  margin-bottom: 5rem;
}

.contributing-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1.5rem;
  margin-top: 3rem;
}

.contributing-card {
  display: flex;
  align-items: center;
  gap: 1.2rem;
  background: var(--bg-tertiary);
  padding: 1.5rem 1.75rem;
  border-radius: 20px;
  text-decoration: none;
  color: var(--text-primary);
  font-weight: 600;
  border: 1px solid transparent;
  transition: var(--transition-smooth);
}

.contributing-card:hover {
  background: var(--bg-secondary);
  border-color: var(--accent-color);
  transform: translateY(-4px);
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.06);
}

.contributing-card-icon {
  font-size: 1.75rem;
  color: var(--accent-color);
  display: flex;
  align-items: center;
  justify-content: center;
}

.contributing-card-text {
  display: flex;
  flex-direction: column;
}

.contributing-card-title {
  font-weight: 700;
  font-size: 1.1rem;
}

.contributing-card-sub {
  font-size: 0.85rem;
  color: var(--text-muted);
  font-weight: 400;
  margin-top: 0.1rem;
}

/* License Section Alert */
.license-alert {
  background: var(--accent-glow);
  border: 1px solid rgba(2, 132, 199, 0.15);
  border-radius: 24px;
  padding: 2.5rem;
  display: flex;
  gap: 2rem;
  align-items: center;
  max-width: 1000px;
  margin: 0 auto;
}

.license-icon {
  font-size: 2.85rem;
  color: var(--accent-color);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.license-info {
  flex-grow: 1;
}

.license-title {
  font-family: var(--font-heading);
  font-size: 1.35rem;
  font-weight: 700;
  margin-bottom: 0.35rem;
}

.license-desc {
  color: var(--text-secondary);
  font-size: 1rem;
  line-height: 1.6;
}

/* Footer styling */
.footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding: 5rem 2rem;
  text-align: center;
}

.footer-content {
  max-width: 900px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
  align-items: center;
}

.footer-logo {
  width: 50px;
  height: 50px;
  border-radius: 12px;
  background: white;
  padding: 2px;
  border: 1px solid var(--border-color);
  margin-bottom: 0.5rem;
}

.footer-brand {
  font-family: var(--font-heading);
  font-weight: 800;
  font-size: 1.65rem;
  color: var(--text-primary);
  margin-top: -0.5rem;
}

.footer-divider {
  width: 60px;
  height: 2px;
  background: var(--accent-color);
  opacity: 0.3;
  border-radius: 2px;
}

.footer-text {
  font-size: 0.85rem;
  color: var(--text-muted);
  line-height: 1.8;
}

.footer-text a {
  color: var(--text-secondary);
  text-decoration: none;
  transition: var(--transition-smooth);
}

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

/* Viewport Scroll Reveal animations */
.scroll-reveal {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.8s cubic-bezier(0.4, 0, 0.2, 1), transform 0.8s cubic-bezier(0.4, 0, 0.2, 1);
}

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

.delay-100 { transition-delay: 100ms; }
.delay-200 { transition-delay: 200ms; }
.delay-300 { transition-delay: 300ms; }
.delay-400 { transition-delay: 400ms; }

/* Responsive Adjustments */
@media (max-width: 992px) {
  .contributing-box {
    padding: 3rem;
  }
}

@media (max-width: 768px) {
  .header-bar {
    top: 1rem;
    width: 95%;
    padding: 0.6rem 1.25rem;
  }
  
  .brand-name {
    font-size: 1.15rem;
  }
  
  .brand-logo-small {
    width: 28px;
    height: 28px;
  }
  
  .lang-toggle-btn {
    padding: 0.4rem 0.85rem;
    font-size: 0.8rem;
  }
  
  .hero-section {
    padding-top: 7rem;
    padding-bottom: 3rem;
  }
  
  .hero-logo {
    width: 120px;
    height: 120px;
    border-radius: 24px;
  }
  
  .container {
    padding: 4rem 0;
  }
  
  .contributing-box {
    padding: 2rem 1.5rem;
  }
  
  .license-alert {
    flex-direction: column;
    text-align: center;
    gap: 1.25rem;
    padding: 2rem;
  }
}