/* Reset */
    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
      font-family: 'Arial', sans-serif;
    }

    /* Background Thiên Hà */
    body {
      background-size: cover;
      color: #e0f7fa;
      line-height: 1.55;
      overflow-x: hidden;
      position: relative;
    }

    /* Overlay mờ */
    body::before {
      content: '';
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      background: rgba(15, 23, 42, 0.85);
      z-index: -1;
    }

    /* Hiệu ứng sao lấp lánh */
		.stars {
		  position: fixed;
		  top: 0;
		  left: 0;
		  width: 100%;
		  height: 100%;
		  pointer-events: none;
		  z-index: -1;
		}

		.star {
		  position: absolute;
		  border-radius: 50%;
		  opacity: 0;
		  animation: twinkle 5s infinite ease-in-out;
		}
		.shooting-star {
		  position: absolute;
		  width: 2px;
		  height: 2px;
		  background: white;
		  border-radius: 50%;
		  filter: blur(1px);
		  opacity: 0;
		  animation: shoot 3s linear forwards;
		}

		.cosmic-ray {
		  position: absolute;
		  width: 1px;
		  height: 1px;
		  background: #81d4fa;
		  border-radius: 50%;
		  opacity: 0;
		  animation: pulseRay 4s infinite;
		}

    .container {
      width: 100%;
      max-width: 100%;
      margin: 0 auto;
      padding: 10px;
    }
	/* Animation cho sao lấp lánh - TỐC ĐỘ CAO */
	@keyframes twinkle {
	  0%, 100% {
		opacity: 0.05;
		transform: scale(0.7);
		background: #4fc3f7;
		box-shadow: 0 0 5px #4fc3f7;
	  }
	  20% {
		opacity: 0.9;
		transform: scale(1.2);
		background: #81d4fa;
		box-shadow: 0 0 8px #81d4fa;
	  }
	  40% {
		opacity: 0.2;
		transform: scale(0.85);
		background: #FFD54F;
		box-shadow: 0 0 6px #FFD54F;
	  }
	  60% {
		opacity: 0.95;
		transform: scale(1.3);
		background: #FFEA00;
		box-shadow: 0 0 12px #FFEA00, 0 0 20px #FFEA00;
	  }
	  80% {
		opacity: 0.1;
		transform: scale(0.75);
		background: #4fc3f7;
		box-shadow: 0 0 5px #4fc3f7;
	  }
	}

	/* Animation cho sao chổi - TẦN SUẤT CAO */
	@keyframes shoot {
	  0% {
		opacity: 0;
		transform: translate(0, 0) scale(0.3);
	  }
	  2% {
		opacity: 1;
		transform: translate(0, 0) scale(1);
	  }
	  100% {
		opacity: 0;
		transform: translate(var(--x), var(--y)) scale(0);
	  }
	}

	/* Animation cho tia sáng vũ trụ - LIÊN TỤC */
	@keyframes pulseRay {
	  0% { opacity: 0; transform: scale(0); }
	  15% { opacity: 0.9; background: #64b5f6; }
	  30% { opacity: 1; transform: scale(2); background: #4fc3f7; }
	  100% { opacity: 0; transform: scale(4); background: #29b6f6; }
	}
    /* Header */
    header {
      text-align: center;
      padding: 5px;
      border-radius: 0 0 12px;
      background: linear-gradient(135deg, rgba(44, 92, 192, 0.85), rgba(76, 175, 80, 0.75));
      backdrop-filter: blur(8px);
      margin-bottom: 5px;
      box-shadow: 0 5px 20px rgba(0, 0, 0, 0.25);
    }

    header .brand {
      font-size: 1.3em;
      font-weight: bold;
      letter-spacing: 1.2px;
      color: #81d4fa;
      text-shadow: 0 0 7px #00b0ff;
    }

    header h1 {
      font-size: 2.2em;
      margin: 8px 0;
      font-weight: 700;
      color: white;
      text-shadow: 0 0 10px rgba(255, 215, 0, 0.6);
    }

    header h1 span {
      color: #FFD700;
      text-shadow: 0 0 12px #FFD700;
    }

    header p {
      font-size: 1.05em;
      color: #b3e5fc;
      max-width: 100%;
      margin: 0 auto;
      text-shadow: 0 0 5px rgba(0, 0, 0, 0.3);
    }

    /* Section */
    section {
  background: transparent;
  backdrop-filter: none;
  padding: 15px;
  border-radius: 10px;
  box-shadow: 
    0 5px 16px rgba(0, 0, 0, 0.25),
    0 0 25px rgba(76, 175, 80, 0.15);
  margin: 15px 0;
  border: 1px solid rgba(100, 200, 255, 0.15);
  transition: all 0.3s ease;
  position: relative;
  overflow: hidden;
}

/* Hiệu ứng viền phát sáng khi hover */
	section::before {
	  content: '';
	  position: absolute;
	  top: 0;
	  left: 0;
	  width: 100%;
	  height: 100%;
	  border-radius: 10px;
	  background: linear-gradient(
		45deg,
		transparent 0%,
		rgba(76, 175, 80, 0.1) 50%,
		transparent 100%
	  );
	  opacity: 0;
	  transition: opacity 0.3s;
	  pointer-events: none;
	}

	section:hover {
	  transform: translateY(-4px);
	  box-shadow: 
		0 8px 20px rgba(0, 0, 0, 0.3),
		0 0 30px rgba(76, 175, 80, 0.25);
	  border-color: rgba(100, 255, 180, 0.3);
	}

	section:hover::before {
	  opacity: 1;
	}

	/* Tối ưu chữ trên nền trong suốt */
	section h2, section h3, section p, section li {
	  text-shadow: 
		0 2px 4px rgba(0, 0, 0, 0.3),
		0 0 8px rgba(76, 175, 80, 0.2);
	  position: relative;
	  z-index: 2;
	}

	/* Viền mờ cho list item */
	li {
	  position: relative;
	  padding-left: 25px;
	}

	li::after {
	  content: '';
	  position: absolute;
	  left: 0;
	  top: 50%;
	  width: 16px;
	  height: 1px;
	  background: linear-gradient(
		90deg, 
		transparent, 
		rgba(76, 175, 80, 0.4), 
		transparent
	  );
	  transform: translateY(-50%);
	}

    h2 {
      color: #64b5f6;
      margin-bottom: 12px;
      padding-bottom: 6px;
      border-bottom: 2px solid rgba(100, 200, 255, 0.2);
      font-size: 1.4em;
      display: flex;
      align-items: center;
      gap: 7px;
    }

    h3 {
      color: #81c784;
      margin: 10px 0;
      font-size: 1.1em;
    }

    ul {
      list-style: none;
      padding-left: 15px;
      margin: 10px 0;
    }

    li {
      margin-bottom: 8px;
      padding-left: 22px;
      position: relative;
      font-size: 0.95em;
    }

    li:before {
      content: "✦";
      color: #4CAF50;
      font-weight: bold;
      position: absolute;
      left: 0;
      top: 0;
    }

    .icon {
      font-size: 1.3em;
      margin-right: 6px;
      vertical-align: middle;
    }

    /* Grid Layout */
    .content-grid {
      display: grid;
      grid-template-columns: repeat(2, 1fr);
      gap: 2px;
    }

    @media (max-width: 768px) {
      .content-grid {
        grid-template-columns: 1fr;
      }
      header h1 {
        font-size: 1.9em;
      }
    }

    /* AI Options - Grid mới */
    .ai-options {
      display: grid;
      grid-template-columns: repeat(2, 1fr);
      gap: 15px;
      margin-top: 12px;
    }

    .ai-box {
      background: rgba(30, 50, 80, 0.6);
      padding: 15px;
      border-radius: 8px;
      border-left: 3px solid #4CAF50;
      transition: all 0.25s;
    }

    .ai-box:hover {
      background: rgba(40, 60, 90, 0.7);
      transform: translateY(-2px);
    }

    .ai-box b {
      color: #a5d8ff;
      display: block;
      margin-bottom: 5px;
    }

    /* Sơ đồ liên kết 2 chiều - Kho ⇄ AI ⇄ Cặp Sách */
    .bidirectional-flow {
      display: flex;
      justify-content: center;
      align-items: center;
      flex-wrap: wrap;
      gap: 5px;
      margin: 15px 0 10px;
      font-size: 0.92em;
      text-align: center;
    }

    .flow-node {
      display: flex;
      flex-direction: column;
      align-items: center;
      min-width: 75px;
    }

    .flow-node i {
      font-size: 1.25em;
      color: #4CAF50;
      margin-bottom: 3px;
    }

    .flow-node span {
      color: #a5d8ff;
      font-weight: 500;
      font-size: 0.88em;
    }

    .flow-arrow {
      color: #4CAF50;
      font-size: 1.2em;
      animation: pulse 2s infinite;
      font-weight: bold;
    }

    @keyframes pulse {
      0%, 100% { opacity: 0.7; transform: scale(1); }
      50% { opacity: 1; transform: scale(1.1); }
    }

    /* CTA */
    .cta {
      text-align: center;
       background: rgb(13 68 43 / 52%);
      backdrop-filter: blur(8px);
      border-radius: 10px;
      padding: 20px 15px;
      margin: 20px 0;
      border: 1px solid rgba(100, 200, 255, 0.15);
    }

    .cta h3 {
      color: white;
      font-size: 1.3em;
      margin-bottom: 15px;
      font-weight: 600;
    }

    .contact-info {
      display: flex;
      justify-content: center;
      gap: 12px;
      flex-wrap: wrap;
      font-size: 0.92em;
    }

    .contact-info a {
      color: #81d4fa;
      text-decoration: none;
      display: inline-block;
      align-items: center;
      gap: 5px;
      padding: 5px 5px;
      border-radius: 6px;
      transition: all 0.25s;
    }

    .contact-info a:hover {
      background: rgba(255, 255, 255, 0.1);
      color: #4fc3f7;
    }

    /* Sticker Liên Hệ */
    .contact-sticker {
      position: fixed;
      bottom: 20px;
      right: 20px;
      background: rgb(14 115 49 / 50%);
      backdrop-filter: blur(8px);
      color: white;
      padding: 10px;
      border-radius: 12px;
      box-shadow: 0 5px 16px rgba(0, 0, 0, 0.3);
      z-index: 1000;
      display: flex;
      flex-direction: column;
      gap: 5px;
      font-size: 0.88em;
      max-width: 260px;
      border: 1px solid rgba(255, 255, 255, 0.12);
    }

    .contact-sticker a {
      color: #fff;
      text-decoration: none;
      display: flex;
      align-items: center;
      gap: 5px;
      font-size: 0.92em;
      padding: 4px 8px;
      border-radius: 6px;
      transition: color 0.25s;
    }

    .contact-sticker a:hover {
      background: rgba(255, 255, 255, 0.08);
      color: #81c784;
    }

    /* Footer */
    footer {
      text-align: center;
      margin-top: 15px;
      padding: 12px;
      color: #64b5f6;
      font-size: 0.8em;
      font-weight: 300;
    }
	
	.logo-container {
	  display: flex;
	  flex-direction: column;
	  align-items: center;
	  justify-content: center;
	  margin: 15px 0 10px;
	  position: relative;
	}

	.logo {
	  height: 30px;
	  max-width: 100%;
	  max-height: 30px;
	  margin-bottom: 0px;
	  transition: all 0.3s ease;
	  object-fit: contain;
	}

	.logo-text {
	  font-size: 2.2em;
	  margin: 8px 0;
	  font-weight: 700;
	  color: white;
	  text-shadow: 0 0 10px rgba(255, 215, 0, 0.6);
	  display: none; /* Ẩn chữ "dBook" khi có logo */
	}

	/* Hiệu ứng hover cho logo */
	.logo:hover {
	  transform: scale(1.03);
	  box-shadow: 0 6px 16px rgba(0, 0, 0, 0.3);
	}

	/* Nếu không có logo, hiển thị chữ dBook */
	.logo[src*="placeholder"] + .logo-text {
	  display: block;
	}

	/* Responsive cho logo */
	@media (max-width: 768px) {
	  .logo {
		max-height: 40px;
	  }
	  
	  .logo-text {
		font-size: 1.9em;
	  }
	}

	@media (max-width: 480px) {
	  .logo {
		max-height: 35px;
	  }
	  
	  .logo-text {
		font-size: 1.7em;
	  }
	}