every 10 minutes:
    loop all players:
        set {_x} to location of loop-player
        set {_resp} to a random integer between 1 and 4
        if {_resp} is equal to 1:
            Increase x-coordinate of {_x} by 20 or 40 or 50
            spawn 1 wither skeleton at {_x}
        if {_resp} is equal to 2:
            Increase x-coordinate of {_x} by -20 or -10 or -15
            spawn 1 wither skeleton at {_x}
        if {_resp} is equal to 3:
            Increase Z-coordinate of {_x} by 20 or 40 or 50
            spawn 1 wither skeleton at {_x}
        if {_resp} is equal to 4:
            Increase z-coordinate of {_x} by -20 or -40 or -50
            spawn 1 wither skeleton at {_x}