anchor.diff:      this.height: 400,
       this.colors: const [
         "#f10","#e20","#d30","#c40","#b50","#a60","#970",
  -      "#880","#790","#6a0","#5b0","#4c0","#3d","#2e0","1f0"],
  +      "#880","#790","#6a0","#5b0","#4c0","#3d0","#2e0","#1f0"],
       this.onClick
     });
   
  
positive.code:         left = x;
        }
      }
      assert(width > left);
      context.fillStyle = prevColor;
      context.fillRect(left, y, width - left, 1);
    }
  
negative.code:       num real = pixelToReal(x);
        int count = probe(real, imag, maxIterations);
  
        String color = "#000";
        if (count < maxIterations) {
          color = colors[count % colors.length];
        }
  
        if (color != prevColor) {
          if (prevColor != null) {
            context.fillStyle = prevColor;
            context.fillRect(left, y, x - left, 1);
          }
  