I love the plus sign, so I chose the plus sign. Why the plus sign? It’s useful + in multiple ways (see what I just did)? Also, none of the examples were available for me to view so I could go in w/ untainted visuals. This is a pretty simple and obvious design, but the plus sign is simple and yet a powerful mathematical idea.

A link: http://www.anitype.com/entry/agtzfmFuaXR5cGVjb3IUCxIHbGV0dGVycxiAgICAlZaNCgw/

A visual:

A code:

Anitype.register('+', {

  author: 'maddy',

  website: 'http://slitscanned.com/',

  construct: function(two, points) {

    var anitype = this;

    var polygon = anitype.makePolygon(points);
    polygon.scale = .5;

    anitype.addTween(polygon, {
      to: { rotation: 3.14/2}, 
      easing: Anitype.Easing.Elastic.Out,
      duration: 1,
      start: 0       
    });
    
    anitype.addTween(polygon, {
      to: { scale: 1},
      easing: Anitype.Easing.Elastic.Out,
      duration: .5, 
      start: 0       
    });
    
    anitype.addTween(polygon, {
      to: { scale: 1}, 
      easing: Anitype.Easing.Elastic.Out,
      duration: .5, 
      start: .5        
    });

    return two.makeGroup(polygon);
  }
});

A sketch: