Program StarScrl_Demo;

(* This program is a replica of StarScroll Demo Copyright Chris Wootton, 1990
   which was published as a 10 Liner in Oct 1990 edition of Amstrad Computer
   User.

   Coding wise a lot of alterations were applied to produce a similar
   program (e.g. an area has been setup in memory for the matrix of the space
   ship and a Screen Hardware Roll has been used to generate the scrolling
   effect), otherwise the main difference in this version is the dreded 'ANY'
   key will Return you to CP/M! :)

   For those interested in the original program can download ACU1990.ZIP and 
   find the original in ACU90B.DSK under the name of STARSCRL.BAS *)


{$C-,U-}
{$I FIRMWARE.LIB}
(* While some routines in this program are CPC Specific, this Library file is
   used to bring additional CPC Specific routines into effect. *)

const ship : array[0..15] of byte =
      (1,1,65,67,71,127,67,1,
       128,128,130,194,226,254,194,128);

var buffer : array[0..15] of byte absolute $AFA0;

Procedure SetupScreen;
Begin

 MODE(0);
 INK(0,0);
 INK(1,26);
 INK(2,26);
 INK(3,13);
 INK(4,6);
 BORDER(0);

End;

Procedure TXTSETMTABLE;
{ This routine sets up a Text Matrix Table
  which points to the Buffer array at $AFA0}
Begin
Inline($11/$FE/$00/
       $21/$A0/$AF/
       $CD/$9B/$BE/
       $AB/$BB);
End;

Procedure SetupShip;
{ This bit of code simply copies the data for the
  Space Ship to the Matrix Area }
var count : byte;
begin
 for count:=0 to 15 do
   mem[$AFA0+count]:=ship[count];
end;

Procedure SCR_HW_ROLL;
{ Used for Scrolling the Screen }
begin
Inline($06/$00/
       $3E/$00/
       $CD/$9B/$BE/
       $4D/$BC);
end;

function testcpm : byte;
{ This program will only run in CP/M v2.2 }
begin
 if (bdos($0c)<>$22) then
  begin
   testcpm:=0;
   writeln('Sorry this program will only run in CP/M 2.2');
  end;
end;

var myship : string[2];
    xpos   : byte;
    xdir   : integer;

BEGIN { Main Routine }
 while (testcpm<>0) do
  begin
   Setupscreen;
   txtsetmtable;
   setupship;
   pen(4);
   myship:=chr(254)+chr(255);
   xpos:=16;
   xdir:=-1;
    Repeat
     xpos:=xpos+xdir;
     case xpos of
       2 : xdir:=1;
      18 : xdir:=-1;
     end;
     grapen(random(3)+1);
     plot(random(638),398);
     SCR_HW_ROLL;
     gotoxy(xpos,25);
     frame;
     write(myship);
     frame;
    until keypressed;
   pen(1);
   mode(2);
   resetcolor;
   testcpm:=0;
end; { While Statement }
END. { Main Routine }