anchor.diff:      var api = event.detail.api;
     });
   
  +  // prevent default keydown action when one of supported key is pressed
  +  document.on.keyDown.add((event) {
  +    if (event.keyCode === 9 || (event.keyCode >= 32 && event.keyCode <= 34 ) || (event.keyCode >= 37 && event.keyCode <= 40)) {
  +      event.preventDefault();
  +    }
  +  })
  +
  +  // trigger impress action (next or prev) on keyup
     document.on.keyUp.add((event) {
       if (event.keyCode === 9 || (event.keyCode >= 32 && event.keyCode <= 34) || (event.keyCode >= 37 && event.keyCode <= 40)) {
         switch (event.keyCode) {
  
positive.code:     }
    });
  
    document.on.click.add((event) {
    });
  
    document.on.click.add((event) {
    });
  
    document.on.touchStart.add((event) {
    });
  
    // rescale presentation when window is resized
  
negative.code: #import('dart:html');
  
  throttle(fn, int delay) {
    int handle = 0;
    return (args) {
      window.clearTimeout(handle);
  