Program ArtExample;
{
          ART DEMONSTRATION PROGRAM  Version 1.00A

     This program demonstrates the use of color graphics
     using TURBO PASCAL on the IBM PC and true compatibles
     with a color graphics adapter.

     INSTRUCTIONS
     1.  Compile and run this program using the TURBO.COM
         compiler.
     2.  Type <ESC> to exit the program, any other key to
         regenerate the screen.
}

const
  MemorySize = 150;

var
  X1, X2, Y1, Y2,
  CurrentLine,
  ColorCount,
  IncrementCount,
  DeltaX1, DeltaY1, DeltaX2, DeltaY2,
  I, Color: integer;
  Ch: char;
  Line: array [1..MemorySize] of record
                                   LX1, LY1: integer;
                                   LX2, LY2: integer;
                                   LColor:  integer;
                                 end;

procedure Check;
var
  ch: char;
begin
  writeln('This program will only work if you have the color graphics adapter installed');
  write('Continue Y/N ');
  repeat
    read (Kbd,Ch)
  until Upcase(Ch) in ['Y','N', #27];
  if Upcase(Ch) in ['N', #27] then
    Halt;
end;

procedure Init;
begin
  for I := 1 to MemorySize do
  with Line[I] do
  begin
    LX1 := 0;
    LX2 := 0;
    LY1 := 0;
    LY2 := 0;
  end;
  X1 := 0;
  Y1 := 0;
  X2 := 0;
  Y2 := 0;
  CurrentLine := 1;
  ColorCount := 0;
  IncrementCount := 0;
  Ch := ' ';
  GraphColorMode;
  Palette(2);
  Color := 2;
  gotoxy(1,25);
  write('Press any key to regenerate, ESC to stop');
end;

procedure AdjustX(var X,DeltaX: integer);
var
  TestX: integer;
begin
  TestX := X+DeltaX;
  if (TestX<1) or (TestX>320) then
  begin
    TestX := X;
    DeltaX := -DeltaX;
  end;
  X := TestX;
end;

procedure AdjustY(var Y,DeltaY: integer);
var
  TestY: integer;
begin
  TestY := Y+DeltaY;
  if (TestY<1) or (TestY>190) then
  begin
    TestY := Y;
    DeltaY := -DeltaY;
  end;
  Y := TestY;
end;

procedure SelectNewColor;
begin
  Color := Random(3)+1;
  ColorCount := 5*(1+Random(10));
end;

procedure SelectNewDeltaValues;
begin
  DeltaX1 := Random(7)-3;
  DeltaX2 := Random(7)-3;
  DeltaY1 := Random(7)-3;
  DeltaY2 := Random(7)-3;
  IncrementCount := 4*(1+Random(9));
end;

procedure SaveCurrentLine;
begin
  with Line[CurrentLine] do
  begin
    LX1 := X1;
    LY1 := Y1;
    LX2 := X2;
    LY2 := Y2;
    LColor := Color;
  end;
end;

procedure Regenerate;
var
  I: integer;
begin
  NoSound;
  GraphColorMode;
  Palette(2);
  for I := 1 to MemorySize do
    with Line[I] do
      Draw(LX1,LY1,LX2,LY2,LColor);
  gotoxy(1,25);
  write('Press any key to continue, ESC to stop');
  read(Kbd,Ch);
end;

procedure WanderingLines;
begin
  repeat
    repeat
      with Line[CurrentLine] do
        Draw(LX1,LY1,LX2,LY2,0);

      if ColorCount=0 then SelectNewColor;
      if IncrementCount=0 then SelectNewDeltaValues;

      AdjustX(X1,DeltaX1);
      AdjustY(Y1,DeltaY1);
      AdjustX(X2,DeltaX2);
      AdjustY(Y2,DeltaY2);

      Draw(X1,Y1,X2,Y2,Color);

      SaveCurrentLine;

      CurrentLine := Succ(CurrentLine);
      if CurrentLine>MemorySize then CurrentLine := 1;
      ColorCount := Pred(ColorCount);
      IncrementCount := Pred(IncrementCount);
    until KeyPressed;
    read(Kbd,Ch);
    if Ch <> #27 then
    begin
      Regenerate;
      gotoxy(1,25);
      write('Press any key to regenerate, ESC to stop');
    end;
  until Ch = #27;
end;

begin
  ClrScr;
  Check;
  Init;
  WanderingLines;
  TextMode;
end.