Animated Loading Button

.button-container {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 150px;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  padding: 20px;
}

.loading-btn {
  position: relative;
  padding: 14px 32px;
  background: #fff;
  border: none;
  border-radius: 50px;
  font-size: 16px;
  font-weight: 600;
  color: #333;
  cursor: pointer;
  overflow: hidden;
  transition: all 0.3s ease;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
  min-width: 120px;
}

.loading-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.15);
}

.btn-text {
  display: inline-block;
  transition: opacity 0.3s ease;
}

.btn-loader {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  opacity: 0;
  transition: opacity 0.3s ease;
}

.spinner {
  width: 20px;
  height: 20px;
  border: 2px solid #f3f3f3;
  border-top: 2px solid #333;
  border-radius: 50%;
  animation: spin 1s linear infinite;
}

.loading-btn.loading .btn-text {
  opacity: 0;
}

.loading-btn.loading .btn-loader {
  opacity: 1;
}

.loading-btn.loading {
  pointer-events: none;
}

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

document.addEventListener('DOMContentLoaded', function() {
  const btn = document.getElementById('loadingBtn');
  
  btn.addEventListener('click', function() {
    // Add loading state
    btn.classList.add('loading');
    
    // Simulate async operation
    setTimeout(() => {
      btn.classList.remove('loading');
      btn.querySelector('.btn-text').textContent = 'Success!';
      btn.style.background = '#4CAF50';
      btn.style.color = 'white';
      
      // Reset after 2 seconds
      setTimeout(() => {
        btn.querySelector('.btn-text').textContent = 'Submit';
        btn.style.background = '#fff';
        btn.style.color = '#333';
      }, 2000);
    }, 3000);
  });
});