public void revert() {
        Tile[][] newLayout = new Tile[layout.length][layout[0].length];
        // Iterate through original and copy the tile values to the new array.
        for (int x = 0; x <= layout.length; x++) {
            for (int y = 0; y <= layout[0].length; y++) {
                newLayout[x][y] = original[x][y].cloneTile();
            }
        }
        // Redirect layout to point to the new array.
        layout = newLayout;
        // TODO: revert player and zombies.
    }