Animated Clouds Background in CSS

  <!-- Sun -->
  <div class="sun"></div>

  <!-- Animated Clouds Background -->
  <div class="clouds-background">
    <!-- Colored Atmospheric Clouds -->
    <div class="colored-cloud colored-1"></div>
    <div class="colored-cloud colored-2"></div>
    <div class="colored-cloud colored-3"></div>
    <div class="colored-cloud colored-4"></div>

    <!-- Large Clouds -->
    <div class="cloud cloud-xl cloud-1"></div>
    <div class="cloud cloud-xl cloud-2"></div>
    <div class="cloud cloud-xl cloud-3"></div>

    <!-- Medium Clouds -->
    <div class="cloud cloud-lg cloud-4"></div>
    <div class="cloud cloud-lg cloud-5"></div>
    <div class="cloud cloud-lg cloud-6"></div>

    <!-- Small Clouds -->
    <div class="cloud cloud-md cloud-7"></div>
    <div class="cloud cloud-md cloud-8"></div>
    <div class="cloud cloud-md cloud-9"></div>

    <!-- Tiny Clouds -->
    <div class="cloud cloud-sm cloud-10"></div>
    <div class="cloud cloud-sm cloud-11"></div>
    <div class="cloud cloud-sm cloud-12"></div>
    <div class="cloud cloud-sm cloud-13"></div>
  </div>

  <!-- Main Content -->
  <div class="content">
    <div class="hero">
      <h1>☁️ Animated Clouds Background</h1>
      <p>Beautiful, smooth, and realistic cloud animations in pure CSS</p>
      <button class="cta-button">Explore More</button>
    </div>

    <div class="features">
      <div class="feature-card">
        <div class="feature-icon">⚡</div>
        <div class="feature-title">High Performance</div>
        <div class="feature-desc">
          Optimized CSS animations running at smooth 60fps with no JavaScript required for maximum efficiency.
        </div>
      </div>

      <div class="feature-card">
        <div class="feature-icon">🎨</div>
        <div class="feature-title">Beautiful Design</div>
        <div class="feature-desc">
          Multiple layers of clouds with varying speeds and sizes create a realistic and immersive sky atmosphere.
        </div>
      </div>

      <div class="feature-card">
        <div class="feature-icon">📱</div>
        <div class="feature-title">Fully Responsive</div>
        <div class="feature-desc">
          Perfectly adapts to all screen sizes and devices while maintaining smooth animations and visual appeal.
        </div>
      </div>
    </div>
  </div>

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

    body {
      font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
      min-height: 100vh;
      overflow-x: hidden;
      position: relative;
      background: linear-gradient(to bottom, #90e0ef 0%, #caf0f8 50%, #ade8f4 100%);
    }

    /* Animated Background Clouds Container */
    .clouds-background {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      overflow: hidden;
      z-index: 1;
    }

    /* Cloud Base Styles */
    .cloud {
      position: absolute;
      background: rgba(255, 255, 255, 0.6);
      border-radius: 100px;
      filter: blur(2px);
    }

    .cloud::before,
    .cloud::after {
      content: '';
      position: absolute;
      background: rgba(255, 255, 255, 0.6);
      border-radius: 100px;
    }

    /* Large Clouds - Slow Movement */
    .cloud-xl {
      width: 350px;
      height: 100px;
    }

    .cloud-xl::before {
      width: 150px;
      height: 120px;
      top: -50px;
      left: 40px;
    }

    .cloud-xl::after {
      width: 180px;
      height: 110px;
      top: -40px;
      right: 40px;
    }

    .cloud-1 {
      top: 5%;
      animation: floatSlow 60s linear infinite;
    }

    .cloud-2 {
      top: 15%;
      animation: floatSlow 70s linear infinite;
      animation-delay: -20s;
    }

    .cloud-3 {
      top: 75%;
      animation: floatSlow 65s linear infinite;
      animation-delay: -40s;
    }

    /* Medium Clouds - Medium Speed */
    .cloud-lg {
      width: 250px;
      height: 80px;
    }

    .cloud-lg::before {
      width: 120px;
      height: 100px;
      top: -45px;
      left: 30px;
    }

    .cloud-lg::after {
      width: 140px;
      height: 90px;
      top: -35px;
      right: 30px;
    }

    .cloud-4 {
      top: 25%;
      animation: floatMedium 50s linear infinite;
      animation-delay: -10s;
    }

    .cloud-5 {
      top: 40%;
      animation: floatMedium 55s linear infinite;
      animation-delay: -30s;
    }

    .cloud-6 {
      top: 85%;
      animation: floatMedium 52s linear infinite;
      animation-delay: -15s;
    }

    /* Small Clouds - Fast Movement */
    .cloud-md {
      width: 180px;
      height: 60px;
    }

    .cloud-md::before {
      width: 90px;
      height: 80px;
      top: -40px;
      left: 20px;
    }

    .cloud-md::after {
      width: 100px;
      height: 70px;
      top: -30px;
      right: 20px;
    }

    .cloud-7 {
      top: 35%;
      animation: floatFast 40s linear infinite;
      animation-delay: -5s;
    }

    .cloud-8 {
      top: 55%;
      animation: floatFast 38s linear infinite;
      animation-delay: -25s;
    }

    .cloud-9 {
      top: 65%;
      animation: floatFast 42s linear infinite;
      animation-delay: -18s;
    }

    /* Tiny Clouds - Very Fast */
    .cloud-sm {
      width: 120px;
      height: 45px;
    }

    .cloud-sm::before {
      width: 60px;
      height: 60px;
      top: -30px;
      left: 15px;
    }

    .cloud-sm::after {
      width: 70px;
      height: 55px;
      top: -25px;
      right: 15px;
    }

    .cloud-10 {
      top: 10%;
      animation: floatVeryFast 30s linear infinite;
      animation-delay: -8s;
    }

    .cloud-11 {
      top: 45%;
      animation: floatVeryFast 32s linear infinite;
      animation-delay: -22s;
    }

    .cloud-12 {
      top: 60%;
      animation: floatVeryFast 28s linear infinite;
      animation-delay: -12s;
    }

    .cloud-13 {
      top: 80%;
      animation: floatVeryFast 35s linear infinite;
      animation-delay: -28s;
    }

    /* Float Animations */
    @keyframes floatSlow {
      0% {
        left: -400px;
        opacity: 0;
      }
      5% {
        opacity: 0.6;
      }
      95% {
        opacity: 0.6;
      }
      100% {
        left: calc(100% + 400px);
        opacity: 0;
      }
    }

    @keyframes floatMedium {
      0% {
        left: -350px;
        opacity: 0;
      }
      5% {
        opacity: 0.7;
      }
      95% {
        opacity: 0.7;
      }
      100% {
        left: calc(100% + 350px);
        opacity: 0;
      }
    }

    @keyframes floatFast {
      0% {
        left: -250px;
        opacity: 0;
      }
      5% {
        opacity: 0.8;
      }
      95% {
        opacity: 0.8;
      }
      100% {
        left: calc(100% + 250px);
        opacity: 0;
      }
    }

    @keyframes floatVeryFast {
      0% {
        left: -200px;
        opacity: 0;
      }
      5% {
        opacity: 0.9;
      }
      95% {
        opacity: 0.9;
      }
      100% {
        left: calc(100% + 200px);
        opacity: 0;
      }
    }

    /* Colored Atmospheric Clouds */
    .colored-cloud {
      position: absolute;
      border-radius: 50%;
      filter: blur(80px);
      opacity: 0.3;
      animation: atmosphericFloat 40s ease-in-out infinite;
    }

    .colored-1 {
      width: 500px;
      height: 500px;
      background: #90e0ef;
      top: 0;
      left: 0;
      animation-delay: 0s;
    }

    .colored-2 {
      width: 600px;
      height: 600px;
      background: #90e0ef;
      top: 30%;
      right: 0;
      animation-delay: -15s;
    }

    .colored-3 {
      width: 450px;
      height: 450px;
      background: #caf0f8;
      bottom: 0;
      left: 20%;
      animation-delay: -25s;
    }

    .colored-4 {
      width: 550px;
      height: 550px;
      background: #90e0ef;
      top: 50%;
      left: 50%;
      animation-delay: -35s;
    }

    @keyframes atmosphericFloat {
      0%, 100% {
        transform: translate(0, 0) scale(1);
      }
      25% {
        transform: translate(100px, -50px) scale(1.1);
      }
      50% {
        transform: translate(-50px, 100px) scale(0.9);
      }
      75% {
        transform: translate(50px, -100px) scale(1.05);
      }
    }

    /* Content Layer */
    .content {
      position: relative;
      z-index: 10;
      min-height: 100vh;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 40px 20px;
    }

    .hero {
      text-align: center;
      color: white;
      text-shadow: 2px 2px 8px rgba(0, 0, 0, 0.3);
      animation: fadeInUp 1s ease;
    }

    .hero h1 {
      font-size: 4rem;
      font-weight: 700;
      margin-bottom: 20px;
      line-height: 1.2;
    }

    .hero p {
      font-size: 1.5rem;
      margin-bottom: 40px;
      opacity: 0.95;
    }

    @keyframes fadeInUp {
      from {
        opacity: 0;
        transform: translateY(50px);
      }
      to {
        opacity: 1;
        transform: translateY(0);
      }
    }

    .cta-button {
      background: rgba(255, 255, 255, 0.95);
      color: #0077b6;
      padding: 18px 40px;
      border: none;
      border-radius: 50px;
      font-size: 1.2rem;
      font-weight: 700;
      cursor: pointer;
      transition: all 0.3s ease;
      box-shadow: 0 8px 30px rgba(0, 0, 0, 0.2);
      text-transform: uppercase;
      letter-spacing: 1px;
      animation: fadeInUp 1s ease 0.3s backwards;
    }

    .cta-button:hover {
      transform: translateY(-5px) scale(1.05);
      box-shadow: 0 12px 40px rgba(0, 0, 0, 0.3);
      background: white;
    }

    /* Feature Cards */
    .features {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
      gap: 30px;
      max-width: 1200px;
      margin-top: 80px;
      width: 100%;
    }

    .feature-card {
      background: rgba(255, 255, 255, 0.85);
      backdrop-filter: blur(10px);
      border-radius: 20px;
      padding: 40px;
      box-shadow: 0 10px 40px rgba(0, 0, 0, 0.15);
      text-align: center;
      transition: all 0.4s ease;
      animation: fadeInUp 1s ease backwards;
      border: 2px solid rgba(255, 255, 255, 0.5);
    }

    .feature-card:nth-child(1) { animation-delay: 0.5s; }
    .feature-card:nth-child(2) { animation-delay: 0.7s; }
    .feature-card:nth-child(3) { animation-delay: 0.9s; }

    .feature-card:hover {
      transform: translateY(-15px) scale(1.02);
      box-shadow: 0 20px 60px rgba(0, 0, 0, 0.25);
      background: rgba(255, 255, 255, 0.95);
    }

    .feature-icon {
      font-size: 4rem;
      margin-bottom: 20px;
      animation: bounce 2s ease-in-out infinite;
    }

    .feature-card:nth-child(2) .feature-icon {
      animation-delay: 0.3s;
    }

    .feature-card:nth-child(3) .feature-icon {
      animation-delay: 0.6s;
    }

    @keyframes bounce {
      0%, 100% {
        transform: translateY(0);
      }
      50% {
        transform: translateY(-10px);
      }
    }

    .feature-title {
      font-size: 1.8rem;
      color: #0077b6;
      font-weight: 700;
      margin-bottom: 15px;
    }

    .feature-desc {
      color: #555;
      line-height: 1.8;
      font-size: 1.1rem;
    }

    /* Sun */
    .sun {
      position: fixed;
      top: 60px;
      right: 80px;
      width: 150px;
      height: 150px;
      background: radial-gradient(circle, #ffd60a 0%, #ffc300 100%);
      border-radius: 50%;
      box-shadow: 0 0 60px rgba(255, 214, 10, 0.6),
                  0 0 100px rgba(255, 214, 10, 0.4),
                  0 0 140px rgba(255, 214, 10, 0.2);
      animation: sunGlow 4s ease-in-out infinite;
      z-index: 2;
    }

    @keyframes sunGlow {
      0%, 100% {
        transform: scale(1);
        box-shadow: 0 0 60px rgba(255, 214, 10, 0.6),
                    0 0 100px rgba(255, 214, 10, 0.4),
                    0 0 140px rgba(255, 214, 10, 0.2);
      }
      50% {
        transform: scale(1.05);
        box-shadow: 0 0 80px rgba(255, 214, 10, 0.8),
                    0 0 120px rgba(255, 214, 10, 0.5),
                    0 0 160px rgba(255, 214, 10, 0.3);
      }
    }

    @media (max-width: 768px) {
      .hero h1 {
        font-size: 2.5rem;
      }

      .hero p {
        font-size: 1.2rem;
      }

      .cta-button {
        padding: 15px 30px;
        font-size: 1rem;
      }

      .features {
        grid-template-columns: 1fr;
        margin-top: 50px;
      }

      .feature-card {
        padding: 30px;
      }

      .sun {
        width: 100px;
        height: 100px;
        top: 40px;
        right: 40px;
      }

      .cloud-xl, .cloud-lg, .cloud-md {
        transform: scale(0.7);
      }
    }