anchor.diff:  2. When particle is next to a cluster it sticks to it.
   3. We start with a simple seed cluster consisting of one particle in the center of the visualisation.
   
  -Model is dead simple. Let's see how we can implement it.
  +Model is dead simple. Let's see how we can implement it and generate some pretty pictures.
   
   == View
   
  
positive.code: - particle_density indicating how many particles will we used ( particle_density x width x height )
  - stopping_fraction as we need to specify some stopping condition for our simulation, we will stop when specified fraction of all particles will be part of the cluster
  
  First we need to create field where particles will be moving:
  
  
  [source,javascript]
  ----
  var CLUSTER = 1;
  
  function createField(width, height) {
  	var field = { width:width, height:height, field: new Uint8Array(width * height)	};
  	field.field[Math.floor(width / 2) + Math.floor(height / 2) * width] = CLUSTER;
  	return field;
  }
  ----
  
negative.code:     particles.y[i] = y;
      
  	if (isNextToCluster(particles, field, i)) {
  		particles.stuck[i] = ++CLUSTER_SIZE;
  		field.field[y*field.width + x] = CLUSTER_SIZE;
  	}
  }
  ----
  