// performs an animated transition between the signup and login controls, or vice-versa
private async Task TransitionToMode(LoginViewModel.Modes mode)
{
var outgoingControls = mode == LoginViewModel.Modes.Login
? SignupControls
: LoginControls;
var incomingControls = mode == LoginViewModel.Modes.Signup
? SignupControls
: LoginControls;
await Task.WhenAll(AvatarImage.FadeTo(0), outgoingControls.FadeTo(0));
outgoingControls.IsVisible = false;
incomingControls.Opacity = 0;
incomingControls.IsVisible = true;
Title = ViewModel.TitleForMode;
await Task.WhenAll(AvatarImage.FadeTo(1), incomingControls.FadeTo(1));
}