const numballs=10;

var xball{numballs},yball{numballs},
    xincr{numballs},yincr{numballs},
    i;

begin
  call cvclear;
  i:=0;
  while i<numballs do
    begin
      while cvx<0 do
        call wait(10);
      xball{i}:=cvx;
      yball{i}:=cvy;
      call cvball(xball{i},yball{i},10);
      xincr{i}:=5;
      yincr{i}:=5;
      call wait(1000);
      i:=i+1
    end;
  while 1=1 do
    begin
      call cvclear;
      i:=0;
      while i<numballs do
        begin
          call cvball(xball{i},yball{i},10);
          xball{i}:=xball{i}+xincr{i};
          if xball{i}<10 then
            if xincr{i}<0 then
              xincr{i}:= -xincr{i};
          if xball{i}>490 then
            if xincr{i}>0 then
              xincr{i}:= -xincr{i};
          yball{i}:=yball{i}+yincr{i};
          if yball{i}<10 then
            if yincr{i}<0 then
              yincr{i}:= -yincr{i};
          if yball{i}>290 then
            if yincr{i}>0 then
              yincr{i}:= -yincr{i};
          i:=i+1
        end;
      call wait(50)
    end
end.