:root {
    --bg-dark: #1b1f24;
    --bg-light: #31363F;
    --text-light: #EEEEEE;
    --accent: #76ABAE;
    --highlight: #3E778C;
    --radius: 10px;
    --transition: 0.3s ease;
  }
  
  * {
    box-sizing: border-box;
    scroll-behavior: smooth;
  }
  
  body {
    margin: 0;
    font-family: 'Segoe UI', sans-serif;
    background-color: var(--bg-dark);
    color: var(--text-light);
  }
  
  /* Header Navbar */
  .navbar {
    background-color: var(--bg-light);
    padding: 1rem 2rem;
    position: fixed;
    top: 0;
    width: 100%;
    z-index: 100;
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
  }
  
  .logo {
    font-weight: bold;
    font-size: 1.2rem;
    color: var(--accent);
  }
  
  /* Nav links default (PC) */
  .nav-links {
    display: flex;
    gap: 1rem;
  }
  
  .nav-links a {
    color: var(--text-light);
    text-decoration: none;
    font-size: 1rem;
    padding: 0.3rem 0.6rem;
    transition: color 0.3s;
  }
  
  .nav-links a:hover,
  .nav-links a.active {
    color: var(--accent);
    border-bottom: 2px solid var(--accent);
  }
  
  /* Hide icons by default on PC */
  .nav-links .icon {
    display: none;
  }
  
  /* Section chung */
  .section {
    min-height: 100vh;
    padding: 8rem 2rem 3rem;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    text-align: center;
  }
  
  .welcome {
    background: linear-gradient(to bottom, #1b1f24, #222831);
  }

  .welcome::after {
    content: "";
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 20vh; /* hoặc 30–50% tùy độ cao muốn phủ */
    z-index: 9; /* Trên các layer parallax, dưới nội dung */
    background: linear-gradient(to top, #1b1f24, transparent); /* tùy chỉnh màu bắt đầu */
    pointer-events: none;
  }
  
  
  /* Products */
  .product-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 2rem;
    margin-top: 2rem;
    max-width: 1100px;
    width: 100%;
  }
  
  .product-card {
    background-color: var(--bg-light);
    padding: 1.5rem;
    border-radius: var(--radius);
    box-shadow: 0 8px 16px rgba(0,0,0,0.3);
    transition: transform var(--transition), box-shadow var(--transition);
  }
  
  .product-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 12px 24px rgba(0,0,0,0.5);
  }
  
  .product-card h3 {
    margin-top: 0;
    color: white;
  }
  
  .product-card p {
    margin-bottom: 1rem;
  }
  
  .product-card button {
    padding: 0.5rem 1rem;
    background-color: var(--highlight);
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color var(--transition);
  }
  
  .product-card button:hover {
    background-color: var(--accent);
  }
  
  /* Pricing */
  .secondary {
    background-color: #2e2e2e;
  }
  
  ul {
    list-style: none;
    padding: 0;
    margin-top: 1rem;
  }
  
  ul li {
    margin: 0.5rem 0;
  }
  
  /* Contact button */
  .contact-button {
    display: inline-block;
    margin-top: 1rem;
    background-color: var(--highlight);
    padding: 0.5rem 1.5rem;
    color: white;
    text-decoration: none;
    border-radius: 5px;
    transition: background-color var(--transition);
  }
  
  .contact-button:hover {
    background-color: var(--accent);
  }
  
  /* Footer */
  footer {
    text-align: center;
    background-color: var(--bg-light);
    padding: 1rem;
    font-size: 0.9rem;
  }
  
  /* Modal */
  .modal {
    display: none;
    position: fixed;
    z-index: 999;
    left: 0; top: 0;
    width: 100%; height: 100%;
    background-color: rgba(0,0,0,0.7);
    justify-content: center;
    align-items: center;
  }
  
  .modal-content {
    background-color: #222831;
    padding: 2rem;
    border-radius: 8px;
    text-align: center;
    width: 90%;
    max-width: 400px;
    color: var(--text-light);
    position: relative;
  }
  
  .close {
    position: absolute;
    right: 1rem;
    top: 1rem;
    font-size: 1.5rem;
    cursor: pointer;
    color: white;
  }

  /* Parallax Layered Background */
.welcome {
    position: relative;
    overflow: hidden;
    min-height: 100vh;
  }
  
  .parallax {
    position: absolute;
    width: 100%;
    height: 100%;
    background-size: cover;
    background-position: center;
    will-change: transform;
    z-index: 1;
    top: 0;
    left: 0;
    opacity: 1;
    pointer-events: none;
  }
  
  .layer1 {
    background-image: url("layer1.png");
    z-index: 1;
  }
  .layer2 {
    background-image: url("layer2.png");
    background-repeat: no-repeat;
    background-position: center top; /* 👈 Đẩy mây lên đỉnh */
    background-size: cover;
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 2; /* Giữ cao hơn layer1, thấp hơn content/layer4 */
  }
  
  .layer3 {
    background-image: url("layer3.png");
    background-repeat: no-repeat;
  background-position: center bottom;
  background-size: cover; /* hoặc contain nếu bạn muốn toàn bộ vừa khung */
  position: absolute;
  bottom: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 4;
  }
  .layer4 {
    background-image: url("layer4.png");
    background-repeat: no-repeat;
    background-position: center bottom;
    background-size: 25%;
    z-index: 5;
  }
  
  .welcome-content {
    position: absolute;
    top: 10%;
    left: 50%;
    transform: translateX(-50%);
    z-index: 3;
    text-align: center;
    color: white;
    width: 100%;
    padding: 1rem;
    text-shadow: 0 2px 6px rgba(0, 0, 0, 0.8);
  }
  
  
  
  /* --------- Mobile Responsive --------- */
  @media (max-width: 768px) {
    .nav-links {
      position: fixed;
      bottom: 0;
      left: 0;
      width: 100%;
      background-color: #2a2f38;
      justify-content: space-around;
      padding: 0.5rem 0;
      z-index: 100;
      box-shadow: 0 -2px 10px rgba(0,0,0,0.3);
      top: auto;
      right: auto;
    }
  
    .nav-links a {
      flex: 1;
      text-align: center;
      font-size: 0.8rem;
      line-height: 1.2;
      padding: 0.3rem 0;
      border: none;
      display: flex;
      flex-direction: column;
      align-items: center;
    }
  
    .nav-links .icon {
      display: block;
      font-size: 1.2rem;
      margin-bottom: 0.2rem;
    }
  
    .nav-links .label {
      display: block;
    }
  
    .nav-links a.active {
      background-color: var(--highlight);
      border-radius: 4px;
    }
  
    .section {
      padding-bottom: 5rem;
    }

    footer {
        margin-bottom: 4.5rem; /* cao hơn chiều cao navbar */
      }
      .layer4 {
        background-size: 35%; /* hoặc 60%, tùy độ cao */
        background-position: center bottom;
      }
  }