function setFlag(){

    //Set Flag randomly on the grid
    var rfX = 0;
    var rfY = 0;
    var currData;

   rfX = Math.floor((Math.random() * gridSizeWidth) + 1);
   rfY = Math.floor((Math.random() * gridSizeHeight) + 1);
   currData = PS.data(rfX, rfY);

   while(currData == "building" || currData == "plane"){
        rfX = Math.floor((Math.random() * gridSizeWidth) + 1);
        rfY = Math.floor((Math.random() * gridSizeHeight) + 1);
        currData = PS.data(rfX, rfY);
    }

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


}