(function() {
    function dropStones(row) {
        for (i = row.length-2; i >= 0; i--) {
            if (row[i] === 'o') {
                var tmpI = i;
                while(row[tmpI + 1] === '.') {
                    row[tmpI] = '.';
                    row[++tmpI] = 'o';
                }
            }
        }
        return row.join("");
    }

    map.forEach(function(row, y) {
        map[y] = dropStones(row.split(''));
    });

    return map;
})();