unit Unit1;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, Forms, Controls, Graphics, Dialogs, StdCtrls, ExtCtrls,
  Math;

type

  Molecule = record
    X, Y: Integer;
    Vx, Vy: Integer;
  end;

  { TForm1 }

  TForm1 = class(TForm)
    Cold: TLabel;
    Warm: TLabel;
    StartStopBtn: TButton;
    Screen: TPaintBox;
    procedure ScreenPaint(Sender: TObject);
    procedure StartStopBtnClick(Sender: TObject);
  private

  public

  end;

var
  Form1: TForm1;
  IsRunning: Boolean = false;

implementation

{$R *.lfm}

procedure TForm1.ScreenPaint(Sender: TObject);
begin

end;

procedure TForm1.StartStopBtnClick(Sender: TObject);
  const RMolecule: Integer = 10; { Радиус молекулы }
  const RHole: Integer = 15;
  const V: Integer = 7; { Скорость молекулы }
  const N = 20; { Количество молекул }

  var angle: Real; { Угол, задающий начальное направление полета }
    i: Integer; { Счетчик цикла }
    Mol: array[1..N * 2] of Molecule; { Массив молекул }
    CurV: Integer; { Выбранаая случайная скорость молекулы }
    halfScreen: Integer;
    T1, T2: Integer; { Температуры и количество, статистика }

begin
  if IsRunning then
  begin
    IsRunning := false;
    StartStopBtn.Caption := 'Пуск';
    Exit;
  end;

  StartStopBtn.Caption := 'Стоп';
  IsRunning := true;

  Randomize;
  Screen.Refresh;

  halfScreen := Screen.Width div 2;
  T1 := V * N;
  T2 := V * N;

  for i := 1 to N * 2 do { Цикл по все молекулам }
  begin
    { Выбор начального положения молекулы }
    if i <= N then
    begin
      Mol[i].X := RandomRange(RMolecule, halfScreen - RMolecule);
    end
    else
    begin
      Mol[i].X := RandomRange(halfScreen + RMolecule,
        Screen.Width - RMolecule);
    end;
    Mol[i].Y := RandomRange(RMolecule, Screen.Height - RMolecule);

    { Выбор нправления и скорости молекулы (1 - V) }
    angle := Random(360) * Pi / 180;
    CurV := RandomRange(1, V);
    Mol[i].Vx := Round(CurV * Sin(angle)); { Получение составляющих }
    Mol[i].Vy := Round(CurV * Cos(angle)); { скорости молекулы }
  end;

  while IsRunning do { Основной цикл }
  begin
    { Черчение перегородки }
    Screen.Canvas.Line(halfScreen, 0, halfScreen,
      Screen.Height div 2 - RHole - RMolecule);
    Screen.Canvas.Line(halfScreen, Screen.Height div 2 + RHole + RMolecule,
      halfScreen, Screen.Height);

    for i := 1 to N * 2 do { Цикл по всем молекулам }
    begin
      Screen.Canvas.Pen.Color := clBtnFace;
      Screen.Canvas.Ellipse(Mol[i].X - RMolecule, Mol[i].Y - RMolecule,
        Mol[i].X + RMolecule, Mol[i].Y + RMolecule);

      { Сдвигаем на новую позицию }
      Mol[i].X := Mol[i].X + Mol[i].Vx;
      Mol[i].Y := Mol[i].Y + Mol[i].Vy;

      if (Mol[i].X > halfScreen - RMolecule) and
        (Mol[i].X - Mol[i].Vx <= halfScreen - RMolecule) then
      begin
        if (Mol[i].Y >= Screen.Height div 2 - RHole) and
          (Mol[i].Y <= Screen.Height div 2 + RHole) then
        begin
            T1 := T1 - V; T2 := T2 + V;
        end
        else
        begin
          Mol[i].X := halfScreen - RMolecule;
          Mol[i].Vx := -Mol[i].Vx;
        end;
      end
      else if (Mol[i].X < halfScreen + RMolecule) and
        (Mol[i].X - Mol[i].Vx >= halfScreen + RMolecule) then
      begin
        if (Mol[i].Y >= Screen.Height div 2 - RHole) and
          (Mol[i].Y <= Screen.Height div 2 + RHole) then
        begin
          T2 := T2 - V;
          T1 := T1 + V;
        end
        else
        begin
          Mol[i].X := halfScreen + RMolecule;
          Mol[i].Vx := -Mol[i].Vx;
        end;
      end;

      { Определяем, не вышла ли молекула за границы аквариума }
      if Mol[i].X > Screen.Width - RMolecule then
      begin
        Mol[i].X := Screen.Width - RMolecule;
        Mol[i].Vx := -Mol[i].Vx;
      end;
      if Mol[i].X < RMolecule then
      begin
        Mol[i].X := RMolecule;
        Mol[i].Vx := -Mol[i].Vx;
      end;
      if Mol[i].Y > Screen.Height - RMolecule then
      begin
        Mol[i].Y := Screen.Height - RMolecule;
        Mol[i].Vy := -Mol[i].Vy;
      end;
      if Mol[i].Y < RMolecule then
      begin
        Mol[i].Y := RMolecule;
        Mol[i].Vy := -Mol[i].Vy;
      end;

      Cold.Caption := IntToStr(T1);
      Warm.Caption := IntToStr(T2);

      Screen.Canvas.Pen.Color := clBlue; { Рисуем молекулу на новой }
      Screen.Canvas.Ellipse(Mol[i].X - RMolecule, Mol[i].Y - RMolecule, { позиции }
        Mol[i].X + RMolecule, Mol[i].Y + RMolecule);
    end;
    Sleep(10); { Пауза на 10 миллисекунд }
    Application.ProcessMessages;
  end;
end;

end.