program asd;

uses
  Graph, crt;


var
  grDriver: Integer;
  grMode: Integer;
  ErrCode: Integer;


  XC,YC:integer;
  i, r: integer;
  f: boolean;

const
  n = 10;
var
  x: array[1 .. n + 1] of integer;
  pnt: array[1 .. n + 1] of PointType;
  scale: real;
  sign: integer;

begin
  grDriver := Detect;
  InitGraph(grDriver, grMode,'');
  ErrCode := GraphResult;
  if ErrCode <> grOk then begin
    Writeln('Graphics error:', GraphErrorMsg(ErrCode));
    halt;
  end;

  XC := GetMaxX div 2;
  YC := GetMaxY div 2;

  R := 75;
  for i:= 1 to n do begin
    x[i] := Trunc(R*Sin(i*2*Pi/n));
    pnt[i].Y := YC+Trunc(R*Cos(i*2*Pi/n));
  end;
  x[n + 1] := x[1];
  pnt[n + 1].Y := pnt[1].Y;

  scale := 1; sign := -1;
  f := false;

  repeat
    setcolor(random(16));
    for i := 1 to n + 1 do
      pnt[i].X := XC + trunc(x[i] * scale);

    drawpoly(n + 1, pnt);
    delay(5000);
    if keypressed then f := true;

    Setcolor(black);
    drawpoly(n + 1, pnt);

    if (scale + sign * 0.1 < 0) or (scale + sign * 0.1 > 1)
    then sign := -sign;

    scale := scale + sign * 0.1;
  Until f;
  CloseGraph;
end.