Slither(action)

function Slither(action)

global fig Maze Row Col sf counter LIJ xb yb uh Sel_Mat Coord Maze_soln;
global ro co rc LinkNum linker CLink;
%--------------------------------------------------------------------------
if nargin < 1,  
    clc
    msg={'Click on the White Lines to solve the puzzle...'};     
    msg_handle=msgbox(msg,'Slither Link','Help');
    pause(3);
    close(msg_handle);
    Slither('Start');
    action='';
end
%--------------------------------------------------------------------------
if strcmp(action,'Start'),  
    linker=0;
    LinkNum=[];
    CLink=[];  
    Row=2+mod(fix(10*rand(1,1)),3);
    Col=2+mod(fix(10*rand(1,1)),3);
    ro=Row; co=Col;
    flag=1;
    
    while flag,
        %Defining Maze
        sf=4;%Scaling Factor
        [Row,Col,Maze]=Maze_Def(Row,Col,sf);

        %Arriving at Maze Boundary
        Maze_Bounds=Boundary(Maze,Row,Col);
        xb=Maze_Bounds(:,1); yb=Maze_Bounds(:,2);
    %     (xb+1)/sf,(yb+1)/sf,

        %Defining SlitherLink Numbers
        Maze_Bounds_Fill=0*Maze;
        Maze_soln=0*Maze;
        for ii=1:length(xb)-1,
            if xb(ii)>xb(ii+1), 
                minr=xb(ii+1); maxr=xb(ii);
            else
                minr=xb(ii); maxr=xb(ii+1);
            end
            if yb(ii)>yb(ii+1), 
                minc=yb(ii+1); maxc=yb(ii);
            else
                minc=yb(ii); maxc=yb(ii+1);
            end
            Maze_Bounds_Fill(minr:maxr,minc:maxc)=1;
        end
        [Maze_Num]=SLN(Row,Col,Maze_Bounds_Fill);
        if ~isempty(find(Maze_Num>1)), flag=0; end
    end
    
    %Displaying the figure
    fig=figure('Name','Slither Link','NumberTitle','off','Visible','off',...
               'units','centimeters');
    
    %creating default GUI buttons
    pos=linspace(0.25*Row,0.75*Row,4);
    uicontrol('units','centimeters','position',[pos(1) 0.5 1 0.75],...
                'string','New','callback','Slither(''New'')',...
                'interruptible','on','BackgroundColor','w');
    
    uicontrol('units','centimeters','position',[pos(2) 0.5 1 0.75],...
                'string','Help','callback','Slither(''Help'')',...
                'interruptible','on','BackgroundColor','w');
        
    uh=uicontrol('units','centimeters','position',[pos(3) 0.5 1 0.75],...
                'string','Ans.','callback','Slither(''Ans.'')',...
                'interruptible','on','BackgroundColor','w');
            
    uicontrol('units','centimeters','position',[pos(4) 0.5 1 0.75],...
                'string','Exit','callback','delete(gcf)',...
                'interruptible','on','BackgroundColor','w');
            
    figure(fig);  
    axis([0 1+(Row+1)/sf 0 1+(Col+1)/sf]);
    hold on
        
    %creating Line-Link Matrix
    Maze_Bounds_Fill_Rot=rot90(Maze_Bounds_Fill);
    Lin_Mat=0*Maze_Bounds_Fill_Rot;
    for ii=1:size(Maze_Bounds_Fill_Rot,1),
        for jj=1:size(Maze_Bounds_Fill_Rot,2),
            if (mod(ii,2)==mod(jj,2) && Maze_Bounds_Fill_Rot(ii,jj)), 
                Lin_Mat(ii,jj)=1; 
            end
        end
    end
    Sel_Mat=0*Lin_Mat;
    
    %drawing Links
    counter=0;
    for ii=1:2/sf:ro,
        for jj=1-1/sf:2/sf:2/sf+co,
            counter=counter+1;
            LIJ(counter)=line(ii+[-1/sf 1/sf],jj+[0 0],'color','w','ButtonDownFcn',{@Callback_Line,counter});
            Coord(counter,:)=[ii jj];
        end
    end
    rc=counter;
    for ii=1:2/sf:co,
        for jj=1-1/sf:2/sf:2/sf+ro,
            counter=counter+1;
            LIJ(counter)=line(jj+[0 0],ii+[-1/sf 1/sf],'color','w','ButtonDownFcn',{@Callback_Line,counter});
            Coord(counter,:)=[jj ii];
        end
    end
    
    %Generating Slither Link Coordinates
    addon=0;
    county=0;
    for ii=1:length(xb)-1,
        if xb(ii)>xb(ii+1), 
            minr=xb(ii+1); maxr=xb(ii);
        else
            minr=xb(ii); maxr=xb(ii+1);
        end
        if yb(ii)>yb(ii+1), 
            minc=yb(ii+1); maxc=yb(ii);
        else
            minc=yb(ii); maxc=yb(ii+1);
        end
        minr=(minr+1)/sf; maxr=(maxr+1)/sf;
        minc=(minc+1)/sf; maxc=(maxc+1)/sf;
        if minr==maxr,
            for jj=minc+1/sf:2/sf:maxc,
                addon=addon+1;
                SLCs(addon,:)=[minr jj]+0/sf;
            end
        else
            for jj=minr+1/sf:2/sf:maxr,
                addon=addon+1;
                SLCs(addon,:)=[jj minc]+0/sf;
            end
        end
    end
%     SLCs
%     plot(SLCs(:,1),SLCs(:,2),'r*');
        
    %Linking Lines & Links
    for ii=1:size(SLCs,1),
        XY=2*SLCs(ii,:)-1;
        county=county+1;
        if floor(XY(1))==XY(1),
            CLink(county)=2*co*(XY(1)-1)+floor(XY(2))+1;
        else
            CLink(county)=rc+2*ro*(XY(2)-1)+floor(XY(1))+1;
        end
    end
    CLink=sort(CLink);

    %Answer
%     line((xb+1)/sf,(yb+1)/sf,'color','b');
%     for ii=2:2:Row,
%         for jj=2:2:Col,
%             plot((ii+1)/sf,(jj+1)/sf,'r*');     
%         end
%     end

    hold off
    axis off;
    axis square;
    axis equal;
    
    %Display Slither Link Numbers
    for ii=3:2:Row,
        for jj=3:2:Col,
            text((ii+1)/sf,(jj+1)/sf,sprintf('%d',Maze_Num(ii,jj)),'color','k');
        end
    end
end
%--------------------------------------------------------------------------
if strcmp(action,'New'), 
    closereq;
    Slither('Start');
end
%--------------------------------------------------------------------------
if strcmp(action,'Help'),
    scrsz = get(0,'ScreenSize');
    Helpfig=figure('Name','Help','NumberTitle','off','Visible','off','BackingStore','off');
    figure(Helpfig);   
    image(imread('Help.jpg'));
    set(Helpfig,'Position',[scrsz(3)/5 scrsz(3)/5 scrsz(3)/1.8 scrsz(4)/1.8]);
    axis off
    if ~waitforbuttonpress,  close(Helpfig);  end
end
%--------------------------------------------------------------------------
if strcmp(action,'Ans.'), 
    if strcmp(get(uh,'string'),'Ans.'),
        %un-drawing Links
        for ii=1:linker,
            set(LIJ(LinkNum(ii)),'color','w');
        end
        for ii=1:length(CLink),
            set(LIJ(CLink(ii)),'color','r');
        end
        set(uh,'string','back','BackgroundColor','y');
    else
        for ii=1:length(CLink),
            set(LIJ(CLink(ii)),'color','w');
        end
        for ii=1:linker,
            set(LIJ(LinkNum(ii)),'color','k');
        end
        set(uh,'string','Ans.','BackgroundColor','w');
    end
end
%--------------------------------------------------------------------------
if strcmp(action,'Exit'), 
    closereq;
end
%--------------------------------------------------------------------------