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

:root {
  --bg-color: #f4f7f9;
  --text-main: #2c3e50;
  --text-muted: #7f8c8d;
  --card-bg: rgba(255, 255, 255, 0.7);
  --card-border: rgba(255, 255, 255, 0.5);
  --shadow-sm: 0 4px 15px rgba(0, 0, 0, 0.03);
  --shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.08);
  --accent: #3498db;
  --accent-hover: #2980b9;
  
  /* Gradients for OS Cards */
  --grad-ios: linear-gradient(135deg, #a1c4fd 0%, #c2e9fb 100%);
  --grad-android: linear-gradient(135deg, #a8e063 0%, #56ab2f 100%);
  --grad-mac: linear-gradient(135deg, #e0c3fc 0%, #8ec5fc 100%);
  --grad-win: linear-gradient(135deg, #89f7fe 0%, #66a6ff 100%);
  
  --grad-btn-1: linear-gradient(135deg, #6a11cb 0%, #2575fc 100%);
  --grad-btn-2: linear-gradient(135deg, #ff6a00 0%, #ee0979 100%);
  --grad-btn-3: linear-gradient(135deg, #86a6c3 0%, #00b0f0 100%);
}

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

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background-color: var(--bg-color);
  color: var(--text-main);
  line-height: 1.6;
  min-height: 100vh;
  position: relative;
  overflow-x: hidden;
}

/* Background Animated Blobs */
.bg-blobs {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  z-index: -1;
  overflow: hidden;
  background: var(--bg-color);
}
.blob {
  position: absolute;
  border-radius: 50%;
  filter: blur(80px);
  opacity: 0.6;
  animation: float 20s infinite alternate;
}
.blob-1 {
  top: -10%; left: -10%;
  width: 50vw; height: 50vw;
  background: #e0c3fc;
}
.blob-2 {
  bottom: -20%; right: -10%;
  width: 60vw; height: 60vw;
  background: #a1c4fd;
  animation-delay: -5s;
}

@keyframes float {
  0% { transform: translate(0, 0) scale(1); }
  100% { transform: translate(50px, 50px) scale(1.1); }
}

.container {
  max-width: 1000px;
  margin: 0 auto;
  padding: 40px 20px;
}

/* Header & Nav */
.header { text-align: center; margin-bottom: 60px; }
.header h1 {
  font-size: 3rem; font-weight: 700; margin-bottom: 15px;
  background: linear-gradient(90deg, #2c3e50, #3498db);
  -webkit-background-clip: text; -webkit-text-fill-color: transparent;
}
.header p { font-size: 1.2rem; color: var(--text-muted); }

.nav-bar { margin-bottom: 30px; }
.nav-bar a {
  text-decoration: none; color: var(--text-muted);
  font-weight: 500; display: inline-flex; align-items: center;
  transition: color 0.3s; padding: 10px 20px;
  background: var(--card-bg); border-radius: 12px;
  backdrop-filter: blur(10px);
}
.nav-bar a:hover { color: var(--accent); background: #fff; }
.nav-bar a::before { content: '←'; margin-right: 8px; font-size: 1.2rem; }

/* Landing Page Grid */
.os-grid {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 30px;
}
.os-card {
  background: var(--card-bg); backdrop-filter: blur(16px);
  border: 1px solid var(--card-border); border-radius: 20px;
  padding: 40px 20px; text-align: center; text-decoration: none;
  color: var(--text-main); box-shadow: var(--shadow-sm);
  transition: all 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
  display: flex; flex-direction: column; align-items: center;
}
.os-card:hover {
  transform: translateY(-10px); box-shadow: var(--shadow-lg); background: rgba(255, 255, 255, 0.9);
}
.os-icon {
  width: 80px; height: 80px; border-radius: 20px;
  display: flex; align-items: center; justify-content: center;
  margin-bottom: 20px; font-size: 40px; color: white;
  box-shadow: 0 4px 15px rgba(0,0,0,0.1);
}
.icon-ios { background: var(--grad-ios); }
.icon-android { background: var(--grad-android); }
.icon-mac { background: var(--grad-mac); }
.icon-win { background: var(--grad-win); }
.os-card h2 { font-size: 1.5rem; font-weight: 600; }

/* Tutorial Page Content */
.tutorial-wrapper {
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(20px); border: 1px solid var(--card-border);
  border-radius: 24px; padding: 40px 50px; box-shadow: var(--shadow-lg);
  margin-bottom: 40px;
}

/* Tabs */
.tabs-nav {
  display: flex; gap: 15px; margin-bottom: 30px;
  background: rgba(0,0,0,0.03); padding: 6px; border-radius: 16px;
}
.tab-btn {
  flex: 1; padding: 12px 20px; border: none; background: transparent;
  border-radius: 12px; font-size: 1rem; font-weight: 600;
  color: var(--text-muted); cursor: pointer; transition: all 0.3s;
}
.tab-btn:hover { color: var(--text-main); }
.tab-btn.active {
  background: white; color: var(--accent); box-shadow: var(--shadow-sm);
}
.tab-content { display: none; animation: fadeIn 0.4s ease; }
.tab-content.active { display: block; }

@keyframes fadeIn { from { opacity: 0; transform: translateY(10px); } to { opacity: 1; transform: translateY(0); } }

/* Typography */
.content-body h2 {
  font-size: 1.6rem; color: #1a1a1a; margin: 35px 0 15px;
  padding-bottom: 10px; border-bottom: 1px solid rgba(0,0,0,0.05);
}
.content-body h3 { font-size: 1.3rem; margin: 20px 0 10px; color: #2c3e50; }
.content-body p, .content-body ul, .content-body ol { margin-bottom: 15px; font-size: 1.05rem; }
.content-body ul, .content-body ol { padding-left: 20px; }
.content-body li { margin-bottom: 8px; }
.content-body a { color: var(--accent); text-decoration: none; font-weight: 500; }
.content-body a:hover { text-decoration: underline; }
.content-body code {
  background: rgba(0,0,0,0.05); padding: 3px 6px; border-radius: 6px;
  font-family: monospace; font-size: 0.9em; color: #d63384;
}

/* Components */
.alert {
  background: #f8f9fa; border-left: 4px solid var(--accent);
  padding: 15px 20px; border-radius: 0 12px 12px 0;
  margin: 20px 0; color: #555; font-size: 0.95rem;
}

.btn-group {
  display: flex; flex-wrap: wrap; gap: 15px; margin: 25px 0;
}
.download-btn {
  display: inline-flex; align-items: center; justify-content: center;
  padding: 12px 28px; border-radius: 12px; color: white !important;
  font-weight: 600; text-decoration: none !important;
  transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
  box-shadow: 0 4px 15px rgba(0,0,0,0.15);
}
.download-btn:hover {
  transform: translateY(-3px); box-shadow: 0 6px 20px rgba(0,0,0,0.2);
}
.download-btn:active { transform: scale(0.96); }
.btn-primary { background: var(--grad-btn-1); }
.btn-secondary { background: var(--grad-btn-2); }
.btn-tertiary { background: var(--grad-btn-3); }

/* Images */
.content-body img {
  max-width: 100%; height: auto; border-radius: 12px;
  box-shadow: var(--shadow-sm); margin: 20px 0;
}
.image-grid {
  display: grid; gap: 15px; margin: 25px 0;
}
.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-4 { grid-template-columns: repeat(4, 1fr); }
.image-grid img { margin: 0; width: 100%; height: auto; }

/* =========================================
   Mobile Optimization
   ========================================= */
@media (max-width: 768px) {
  .container {
    padding: 20px 15px;
  }
  
  .header h1 {
    font-size: 1.8rem;
  }
  
  .header p {
    font-size: 1rem;
  }
  
  .os-grid {
    grid-template-columns: 1fr;
  }
  
  .tutorial-wrapper {
    padding: 25px 20px;
  }
  
  .tabs-nav {
    flex-direction: column;
    gap: 10px;
  }
  
  .tab-btn {
    padding: 12px 15px;
    font-size: 0.95rem;
  }
  
  .content-body h2 {
    font-size: 1.35rem;
    margin: 25px 0 15px;
  }
  
  .content-body h3 {
    font-size: 1.15rem;
  }
  
  .content-body p, .content-body ul, .content-body ol {
    font-size: 0.95rem;
  }
  
  /* Buttons stacking on mobile */
  .btn-group {
    flex-direction: column;
    gap: 12px;
  }
  
  .download-btn {
    width: 100%;
    text-align: center;
  }
  
  /* Grid images handling on mobile */
  .image-grid.grid-3, .image-grid.grid-4 {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 480px) {
  /* On very small screens, make desktop screenshots 1 per row, but keep mobile screenshots 2 per row if possible.
     Since we can't easily distinguish, we will make everything 1 column EXCEPT if it's explicitly a grid-4 (which are usually tall thin mobile screenshots). */
  .image-grid.grid-2 {
    grid-template-columns: 1fr;
  }
}