  polynomial_context.fillStyle="#d64562";
    for(var i = 0; i < polynomial_n; ++i){
        const xi = x_to_client(polynomial_xs[i]) + 0.5;
        const yi = y_to_client(polynomial_ys[i]) + 0.5;
        polynomial_context.beginPath();
        polynomial_context.arc(xi, yi, 4, 0, 2*Math.PI);
        polynomial_context.stroke();
        polynomial_context.fill();
        polynomial_context.closePath();
    }
    polynomial_context.stroke();
    polynomial_context.closePath();

    // guides
    if(do_guides