function setFlag(){

    //Set Flag randomly on the grid
    var rfX = 0;
    var rfY = 0;
    var currData = PS.data(rfX, rfY);

    while(currData == "building" || currData == "plane"){
        rfX = PS.random(gridSizeWidth);
        rfY = PS.random(gridSizeHeight);
        currData = PS.data(rfX, rfY);
    }

    PS.glyph(rfX, rfY, "⌲");
    PS.glyphColor(rfX,rfY, PS.COLOR_GREEN);


}