add bonus stack cleaning on new round
add bonus stack cleaning on new round

lutangar/curvytron,Elao/curvytron-arcade,Curvytron/curvytron,Elao/curvytron,Elao/curvytron,Elao/curvytron-arcade,coredump-ch/curvytron,lutangar/curvytron,Curvytron/curvytron-arcade,Curvytron/curvytron-arcade,Curvytron/curvytron,coredump-ch/curvytron,Wohops/curvytron,Wohops/curvytron