ver_1_eq_2[0], solver_1_eq_2[1], solver_1_eq_2[2]);
            cur_y = projected_y(prev_x, prev_y, solver_1_eq_2[0], solver_1_eq_2[1], solver_1_eq_2[2]);
        }
        context.lineTo(x_to_client(cur_x), y_to_client(cur_y));
    }
    last_iterations = i;
    context.strokeStyle="#002200";
    context.setLineDash([2, 2]);
    context.stroke();
    context.setLineDash([]);
    context.closePath();

    // grid
    draw_grid_on(context);

    // mouse move
    if(do_guides){
        if(document.getElement