body {
  font-family: 'Poppins', sans-serif;
  background-color: #f4f6f8;
  min-height: 100vh;
  margin: 0;
  display: flex;
  flex-direction: column;
}

.main-content {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 40px 20px;
}

/* Thêm responsive cho nav và footer */
@media (max-width: 768px) {
  .nav-links {
    display: none;
  }
}

.quiz-container {
  background-color: #fff;
  padding: 40px;
  width: 100%;
  max-width: 800px;
  border-radius: 16px;
  box-shadow: 0 8px 16px rgba(0, 0, 0, 0.1);
  text-align: center;
  position: relative;
}

.quiz-title {
  font-family: 'Playfair Display', serif;
  color: #222;
  font-size: 36px;
  font-weight: 700;
  text-align: center;
  margin-bottom: 24px;
  background: linear-gradient(45deg, #007bff, #00bcd4);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.question {
  font-size: 22px;
  font-weight: 600;
  color: #444;
  margin-bottom: 16px;
  text-align: left;
}

.options {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.option {
  background-color: #f6f8fa;
  border: 2px solid #e1e4e8;
  border-radius: 10px;
  padding: 14px 18px;
  font-size: 18px;
  font-weight: 500;
  color: #333;
  cursor: pointer;
  transition: all 0.3s ease;
  text-align: left;
}

.option:hover {
  background-color: #e6efff;
  border-color: #6aa8ff;
  transform: translateY(-2px);
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

.option.selected {
  background-color: #d6e9ff;
  border-color: #007bff;
  font-weight: 600;
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0, 123, 255, 0.2);
}

.input-group {
  margin: 20px 0;
  text-align: left;
}

.input-group label {
  display: block;
  margin-bottom: 8px;
  color: #555;
  font-weight: 500;
}

input {
  font-size: 16px;
  padding: 12px;
  border-radius: 8px;
  border: 2px solid #e1e4e8;
  margin: 8px 0;
  width: 100%;
  max-width: 400px;
  transition: all 0.3s ease;
}

input:focus {
  border-color: #007bff;
  box-shadow: 0 0 0 3px rgba(0, 123, 255, 0.1);
  outline: none;
}

button {
  background: linear-gradient(45deg, #007bff, #00bcd4);
  color: white;
  font-weight: 600;
  font-size: 16px;
  padding: 14px 28px;
  border-radius: 8px;
  border: none;
  cursor: pointer;
  transition: all 0.3s ease;
  width: 100%;
  max-width: 400px;
  margin-top: 20px;
}

button:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0, 123, 255, 0.2);
}

.score {
  font-size: 20px;
  font-weight: 600;
  position: fixed;
  top: 20px;
  right: 20px;
  background: linear-gradient(45deg, #007bff, #00bcd4);
  color: white;
  padding: 12px 24px;
  border-radius: 50px;
  box-shadow: 0 4px 12px rgba(0, 123, 255, 0.2);
}

/* Loading Animation */
.loading-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  
  background: rgba(255, 255, 255, 0.9);
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: 1000;
  backdrop-filter: blur(5px);
}

.loading-spinner {
  width: 50px;
  height: 50px;
  border: 5px solid #f3f3f3;
  border-top: 5px solid #007bff;
  border-radius: 50%;
  animation: spin 1s linear infinite, scale 2s ease-in-out infinite;
}

.loading-text {
  position: absolute;
  margin-top: 80px;
  color: #007bff;
  font-weight: 600;
  font-size: 18px;
  animation: pulse 1.5s ease-in-out infinite;
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

@keyframes scale {
  0%, 100% { transform: scale(1) rotate(0deg); }
  50% { transform: scale(1.2) rotate(180deg); }
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.5; }
}