code: function (params) {
          return new hitagi.Entity()
              .attach(new hitagi.components.Position({
                  x: params.x,
                  y: params.y
              }))
              .attach(new hitagi.components.Velocity({xspeed: 0, yspeed: 0}))
              .attach(new hitagi.components.graphics.Graphic({
                  scale: {
                      x: 0.45,
                      y: 0.45
                  }
              }))
              .attach(new hitagi.components.graphics.Sprite({
                  animationSpeed: 0.12,
                  path: [
                      'http://hitagi.s3-website-eu-west-1.amazonaws.com/bird_0.png',
                      'http://hitagi.s3-website-eu-west-1.amazonaws.com/bird_1.png',
                      'http://hitagi.s3-website-eu-west-1.amazonaws.com/bird_2.png'
                  ]
              }))
              .attach({
                  $id: 'gravity',
                  magnitude: 0,
                  terminal: 12
              })
              .attach({
                  $id: 'bird',
                  flapSpeed: 10
              })
              .attach(new hitagi.components.Collision({
                  height: 18,
                  width: 32
              }));
      }
docs: Define entities.