     ctx.strokeStyle = '#F00';
        diagram.arrow(ctx, 0, 0, 0, 40, false, true, 0.5);
        ctx.restore();
      }

      dots.push({
        dot,
        r: r,
      });
    }

    {
      ctx.strokeStyle = 'black';
      ctx.fillStyle = 'brown';
      diagram.drawEye(ctx, lx, ly, width / 10, height / 10);

      ctx.save();
      ctx.translate(sx, sy);
      ctx.rotate(direction);

      const gradient = ctx.createLinearGradient(-surfaceWidth / 2, 0, surfaceWidth / 2, 0);
      const numPoints = 5;
