function portalSpeedGo(numPairs)

if nargin < 1
    numPairs = 110;
end

isIn = @(idxVar, array) any(array == idxVar) == 1;

floor = zeros(1, 1, 3);
floor(:) = 212;
portal = zeros(1, 1, 3);
portal(1) = 202;
portal(2) = 192;
boost = zeros(1, 1, 3);
boost(1) = 255;
boost(2) = 255;

floorTiles = zeros(0);

cdata = imread('WarpSpeed.png');

%spawning area
blueRows = 8:12;
blueCols = 51:55;
redRows = 28:32;
redCols = 7:11;

%loop over inside area, keeping the outside paths clear
for i = 5:35
    for j = 5:57
        %keep spawning tiles clear
        if (isIn(i, blueRows) && isIn(j, blueCols)) || (isIn(i, redRows) && isIn(j, redCols))
            continue;
        end
        pixel = cdata(i, j, :);
        if isequal(pixel, floor)
            floorTiles = [floorTiles, [i; j]];
        end
    end
end

%pick just few enough to stay under the JSON file size limit
%Subtracting one because javascript has 0-based arrays
floorTiles = floorTiles(:,randperm(size(floorTiles, 2)));
portalTiles = floorTiles(:, numPairs+1:2*numPairs) - 1;
floorTiles = floorTiles(:, 1:numPairs) - 1;

%make new image file
for n = 1:numPairs
    loc = floorTiles(:, n) + 1;
    cdata(loc(1), loc(2), :) = portal;
    
    loc = portalTiles(:, n) + 1;
    cdata(loc(1), loc(2), :) = portal;
end

%make portal-only version
portalsOnly = cdata;
for i = 1:size(cdata, 1)
    for j = 1:size(cdata, 2)
        if isequal(portalsOnly(i, j, :), boost)
            portalsOnly(i, j, :) = floor;
        end
    end
end

%write JSON file
fid = fopen('PortalSpeed.json', 'w');
fprintf(fid, '{');
fprintf(fid, '"info": {\n"name": "PortalSpeed",\n "author": "BBQchicken"\n},\n');
fprintf(fid, '"portals": {\n');

for i = 1:size(floorTiles, 2)
    source = ['"', num2str(floorTiles(2, i)), ',',...
        num2str(floorTiles(1, i)), '"'];
    destination = [' "x": ', num2str(portalTiles(2, i)), ', "y": '...
        num2str(portalTiles(1, i))];
    line = [source, ': { "destination": { ', destination, ...
        ' } },\n'];
     fprintf(fid, line);
     
     %Then do reverse direction
     source = ['"', num2str(portalTiles(2, i)), ',',...
        num2str(portalTiles(1, i)), '"'];
    destination = [' "x": ', num2str(floorTiles(2, i)), ', "y": '...
        num2str(floorTiles(1, i))];
    line = [source, ': { "destination": { ', destination, ...
        ' } }'];
     
    if i ~= size(floorTiles, 2)
        line = [line, ',\n'];
    else
        line = [line, '\n'];
    end
    fprintf(fid, line);
end

fprintf(fid, '}\n');
fprintf(fid, '}');

imwrite(cdata, 'PortalSpeed.png');
imwrite(portalsOnly, 'PortalsOnly.png');

disp('Maps are ready!');