Uses Graph,Crt;
Const m = 18;
      n = 18;
      Left  = #75;
      Right = #77;
      Space = #32;
      Mouses = 10;

Var
   GD,GM,Size: Integer;
   x0,y0,x1,y1,r: Integer;
   t: Real;
   HunterAngle, TargetAngle: real;

Function Angle(x,y: Real): Real;
Var Theta: Real;
Begin
  If (x=0.0) AND (y=0.0) Then
     Angle:=-1.0
  Else If x=0.0 Then
     Begin
       If y>0
          Then Angle:=0.5*Pi
          Else Angle:=1.5*Pi;
     End
  Else
     Begin
       Theta:=ArcTan(y/x);
       If x>0.0 Then
          Begin
            If y>0.0
               Then Angle:=Theta
               Else Angle:=2*Pi+Theta;
          End
       Else Angle:=Pi+Theta;
     End;
End;

Procedure InitHunter;
Begin
     x0:=320;
     y0:=240;
     r:=20;
     x1:=r+x0;
     y1:=y0;
     t:=0;
End;

Procedure DrawHunter(KC: Char);
Begin
     Case KC Of
      Left:  t:=t-0.1;
      Right: t:=t+0.1;
     End;
     
     If (t>=2*Pi) Or (t<=-2*Pi) Then t:=0;
     SetColor(Black);
     Line(x0, y0, x1, y1);
     x1:=Round(r*cos(t))+x0;
     y1:=Round(r*sin(t))+y0;
     SetColor(Red);
     Line(x0,y0,x1,y1);
     SetColor(Blue);
     SetFillStyle(1,Blue);
     PieSlice(320,240,0,360,10);
     SetColor(Red);
     SetFillStyle(1,Red);
     PieSlice(320,240,0,360,6);
     
     HunterAngle:=Angle(x1-320,240-y1);
     gotoxy(35, 23);
     write('Hunter: ',HunterAngle:10:7);
End;

Procedure DrawTarget;
var Xt,Yt: integer;
    Delta: real;
Begin
     Xt := 50;
     Yt := 70;

     TargetAngle:=Angle(Xt-320,240-Yt);
     gotoxy(1, 1);
     write('Target: ', TargetAngle:10:7);

     Delta := Abs(HunterAngle-TargetAngle);

     gotoxy(1, 2);
     write('Delta: ', Delta:10:7);


     if Delta < 0.1
        then SetColor(12)
        else SetColor(15);

     Circle(Xt,Yt,10);
End;

Procedure Main;
Var Tm: Real;
    i,Count: Integer;
    c: Char;
Begin
     Tm:=0;
     Count:=0;

     Repeat
           Tm:=Tm+1;
           c:=#0;

           While KeyPressed Do c:=ReadKey;

           If (c=Left) Or (c=Right) Then
              begin
                DrawHunter(c);
                DrawTarget;
              end;

     Until c=#27;
     
     RestoreCrtMode;
End;

Begin
     GD:=Detect;
     InitGraph(GD,GM,'');
     Randomize;
     InitHunter;
     directvideo := false;
     DrawHunter(Left);
     DrawTarget;
     Main;
End.