Multilayer world

    local world = display.newGroup()
    group:insert(world)
    local movable = display.newGroup()
    group:insert(movable)
    for i=1, 8 do
        for j=1, 8 do
            local value = gameMap[i][j]
            if tileFactory[value] then
                local mobile
                gameMap[i][j], mobile = tileFactory[value](i, j)
                world:insert(gameMap[i][j])
                if mobile then
                    movable:insert(mobile)
                end
            end
        end
    end