   request.show().then(function(paymentResponse) {
          // Here we would process the payment. For this demo, simulate immediate success:
          paymentResponse.complete('success')
            .then(function() {
              // For demo purposes:
              introPanel.style.display = 'none';
              successPanel.style.display = 'block';
            });

        }).catch(function(error) {
          // Handle cancelled/failed payment. Fall back to legacy form. For demo purposes:
          int