function MLogo(Lname,opts)
    % MLogo(Lname,opts)
    % Lname = 'dragon', 'Hilbert', 'Gosper', or 'plant'
    % https://blogs.mathworks.com/cleve/2025/05/03
    % Copyright, 2025, MathWorks
    arguments
        Lname string
        opts.maxlevel double
        opts.color double
        opts.start string = 'A'
        opts.delta double = 90
        opts.dirstart double = 0
        opts.shave logical = false
    end

    [Arule,Brule] = rules(Lname);
    [maxlevel,color,delta,start,dirstart,shave] = set_opts(Lname,opts);

    expd = @(dir) cosd(dir) + 1i*sind(dir);
    paws = @(p) pause(p);
    % paws = @(p) gif_frame;

    s = start;
    for level = 1:maxlevel
        stack = zeros(0,2);
        z = 0;
        dir = dirstart;
        sloop = s;
        s = '';
        zees = zeros(0,1);
        for kase = sloop
            switch kase
                case 'A'
                    s = [s Arule];

                case 'B'
                    s = [s Brule];

                case 'F' % step
                    z = z + expd(dir);
                    zees = [zees, z];
                    s = [s 'F'];

                case '+' % turn right
                    dir = dir + delta;
                    s = [s '+'];

                case '-' % turn left
                    dir = dir - delta;
                    s = [s '-'];

                case '['  % push stack
                    stack = [z dir; stack];
                    s = [s '['];
                    
                case ']'  % pop stack
                    z = stack(1,1);
                    dir = stack(1,2);
                    zees = [zees, z];
                    stack(1,:) = [];
                    s = [s ']'];
            end
        end
        if shave
            zees = shaver(zees);
        end
        plotzees(zees,level,Lname,color)  
        paws(1)
    end

    function [Arule,Brule] = rules(Lname)
        switch lower(Lname)
            case 'gosper'
                Arule = 'A+BF++BF-FA--FAFA-BF+';
                Brule = '-FA+BFBF++BF+FA--FA-B';
            case 'dragon'
                Arule = 'A+BF+';
                Brule = '-FA-B';
            case 'hilbert'
                Arule = '+BF-AFA-FB+';
                Brule = '-AF+BFB+FA-';
            case 'plant'
                Arule = 'AF[+AF]AF[-AF][AF]';              
                Brule = '';
        end
    end

    function [maxlevel,color,delta,start,dirstart,shave] = ...
            set_opts(Lname,opts)
        switch lower(Lname)
            case 'gosper'
                opts.delta = 60;
                maxlevel = 5;
                color = gcaco(2);
            case 'dragon'
                maxlevel = 12;
                color = gcaco(4);
            case 'hilbert'
                maxlevel = 6;
                color = gcaco(1);
            case 'plant'
                opts.delta = -45;
                opts.dirstart = 90;
                maxlevel = 7;
                color = gcaco(5);
            otherwise
                error([Lname ' not recognized.'])
        end
        if isfield(opts,'delta'), delta = opts.delta; end
        if isfield(opts,'dirstart'), dirstart = opts.dirstart; end
        if isfield(opts,'shave'), shave = opts.shave; end
        if isfield(opts,'start'), start = opts.start; end
        if isfield(opts,'maxlevel'), maxlevel = opts.maxlevel; end
        if isfield(opts,'color'), color = opts.color; end

    end

    function plotzees(zees,level,Lname,color)
        shg
        plot(zees,'linewidth',2,'color',color)
        axis padded
        axis equal
        noticks
        box on
        title(sprintf('%s    %d',Lname,level),'fontsize',14)
    end

    function u = shaver(z)
        % shaver(z), flatten sharp corners
        if ~isempty(z)
            u = z(1);
            for j = 2:length(z)
                u = [u z(j-1)+[1 9]/10*(z(j)-z(j-1))];
            end
            u(end+1) = z(end);
        else
            u = z;
        end
    end
end