Flying block

blockit.js

(function($){
  $.extend($.fn,{
    blockit: function(options){
      new BlockIt(this, options);
      return this;
    }
  });

  var BlockIt = function(el, options){
    var options = options || {},
      posLeft = (options['left'] || (this.offset(el).left + (el.width()/2))) - 24,
      posTop = (options['top'] || (this.offset(el).top + (el.height()/2))) - 24;

    this.position = [posLeft,posTop]
    this.windowSize = [$('body').width(), $('body').height()]
    this.showTarget();
    var that = this;
    setInterval(function(){that.fire.call(that)},300);
  };

  $.extend(BlockIt.prototype,{
    offset : function(el){
      var _offset = {};
      this.offset = function(el){
         var s = el
        _offset[s] = _offset[s] || el.offset();
        return _offset[s]
      };
      return this.offset;
    }(),

    showTarget : function(){
      var target = $('<img src=http://cdn1.iconfinder.com/data/icons/cc_mono_icon_set/blacks/48x48/target.png />');
      target.css({
        'position' : 'absolute',
        'left' : this.position[0] + 'px',
        'top' : this.position[1] + 'px'
      });
      $('body').append(target);
    },

    coinFlip : function(){
      return !!parseInt(Math.random() * 2, 10);
    },

    fire : function(){
      var d = $('<div />');
      if(this.coinFlip()) {
        // coming from left or right
        d.css({
          "top" : parseInt(Math.random()*this.windowSize[1],10) + 'px',
          "left" : (this.coinFlip() ? (-25) : (this.windowSize[0] + 25) ) + 'px'
        });
      } else {
        // coming from top or bottom
        d.css({
          "left" : parseInt(Math.random() * this.windowSize[0],10) + 'px',
          "top" : (this.coinFlip() ? (-25) : (this.windowSize[1] + 25) ) + 'px'
        });
      }
      d.css({
        "position" : "absolute",
        "height" : "10px",
        "width" : "10px",
        "border" : "1px solid green"
      });

      $('body').append(d);
      var that = this;
      setTimeout(function(){
        d.animate({
          "top" : (19+that.position[1]) + "px",
          "left" : (19+that.position[0]) + "px"
        }, 6000,function(){$(this).remove()});
      }, 300);
    }
  });
})(jQuery);

bookmarklet

javascript:(function(){var d = document;if(window.jQuery){jQuery.getScript('https://raw.github.com/gist/1158340/blockit.js')}})()