docs: public void addPointToTail( int x , int y ) {
  		int index = tail.start + tail.length*2;
  
  		int block[];
  		int blockIndex = tail.block + index/blockLength;
  		if( blockIndex == blocks.size ) {
  			tailBlockSize = 0;
  			block = blocks.grow();
  		} else {
  			block = blocks.get( blockIndex );
  		}
  		tailBlockSize += 2;
  		index %= blockLength;
  
  		block[index ] = x;
  		block[index+1 ] = y;
  		tail.length += 1;
  	}