The ng-click
directive should be on the button where you click not on the tag where you want to show the result.
You don't need your query('#letter_A').onClick.listen(...
when you use ng-click
they have similar functionality.
You need to place the controller keyboard
so that your buttons and the <div>
where you want to show the output are within the tag where the controller is applied.
Try it and if it doesn't work update your question with the new code and I'll take another look.