Help Space Invaders Shooting

[psycho]

As the title implies, I need help with programming in the shooting function for the space ship. I'm supposed to program a Space Invaders clone in good ol' pascal using non other than the CRT library; that means no graphics, just characters to interpret the game's graphics. As of now I managed to code-in the spacebar function to create the bullet, but what I want to do now is to move the bullet upwards.

USES crt;

CONST
	max_row = 40;  //Matrix dimensions
	max_col = 80;
    Spacebar = #32;

// Can_Shoot checks the posibility to shoot, not yet implemented
//	Shooting checks if the user y pressing the spacebar key 
PROCEDURE Bullet_Creation(var Can_Shoot : boolean; var Shooting : char);
BEGIN
REPEAT
        Shooting := readkey;
			IF Shooting = Spacebar AND Can_Shoot THEN
				BEGIN
                 gotoxy(9,9);

                 writeln('I');
                 Can_Shoot := false;
				END;
UNTIL keypressed;

END;

// Main Program
var Can_Shoot : boolean;
  Shooting : char;
  MATRIX : ARRAY[1..max_row,1..max_col] OF char;
  i,j : byte;
BEGIN
	Bullet_Creation(Can_Shoot,Shooting);


	//Print Matrix
  for i:=1 to max_row do
  begin
  for j:=1 to max_col do
   write (MATRIX[i,j]);
  writeln;
  end;

    readln();

END.

Thanks in advance!
Psycho.

PD: As you can see, the gameplay field is supposed to be a matrix.

[chronozphere]

You should make a (dynamic) array containing information about all the bullets. Something like this:

[pascal]
TBullet = record
Used: Boolean; //Whether the bullet is in use (visible and moving)
X,Y: Integer; //Position of the bullet
DX,DY: Integer; //Direction in which the bullet travels (you can leave this out when you want all bullets to travel upwards).
//etc etc...
end;

MyBullets: array of TBullet;
[/pascal]

Once in a while, you should loop through this array and move all the bullets one step. After you have done this (or before you make the step), you should check if the bullet has hit something.

Good luck

[psycho]

Ok I kinda get what you're saying, what I don't understand is how do I make it go through the array if i have not defined the array's dimension?
And I came up with a different scheme, basically with a For loop I make it write the bullet one step up and then one step down I make it erase it. The only problem is that the bullet goes down instead of going up...

PROCEDURE Bullet_Creation(var Shoot : char);

var X,Y : integer;
BEGIN
X := 20; 
        
        Shoot := readkey;
						IF Shoot = Spacebar THEN
							BEGIN
								FOR Y:= 0 to max_col DO
									BEGIN
            		GOTOXY(X,Y+1);
            		writeln('|');
            		
            		GOTOXY(X,Y-1);
            		writeln(' ');
            		delay(50);	
									END;
           END;
       

END;

Thanks again! hope you can cooperate...

[pjpdev]

Ok I kinda get what you're saying, what I don't understand is how do I make it go through the array if i have not defined the array's dimension?
And I came up with a different scheme, basically with a For loop I make it write the bullet one step up and then one step down I make it erase it. The only problem is that the bullet goes down instead of going up...

PROCEDURE Bullet_Creation(var Shoot : char);

var X,Y : integer;
BEGIN
X := 20; 
        
        Shoot := readkey;
						IF Shoot = Spacebar THEN
							BEGIN
								FOR Y:= 0 to max_col DO
									BEGIN
            		GOTOXY(X,Y+1);
            		writeln('|');
            		
            		GOTOXY(X,Y-1);
            		writeln(' ');
            		delay(50);	
									END;
           END;
       

END;

Thanks again! hope you can cooperate...

Do it the other way around. Remember that the Y axis moves from top to bottom, so you should minus to move to the top.

[pascal]
GOTOXY(X, Y-1);
writeln('|');

GOTOXY(X, Y+1);
writeln(' ');
delay(50);
[/pascal]

[psycho]

GREAT!!! Finally got it goin' !!
Now, there's one more thing I want to establish before I leave...
I know that sooner or later I will have to check for collisions and I am supposed to make the bullet go through the matrix, all I'm doing here with the gotoxy is printing it on a given coordinate.
What I want to know is:
Is it possible for the bullet to go through the columns of the matrix?
For instance 'J = J + 1' I don't know, make it take a step through the dimensions.

[User137]

Do not draw anything on screen at Bullet_Creation, instead draw all bullets same time in the main loop. You should have the coordinates of each bullet saved in array.

There is example of using dynamic array (i am not sure if all pascal compilers support this, especially oldest):
http://www.delphibasics.co.uk/RTL.asp?Name=Array

But you can just define, say 100 bullets max and have the array size static. If you can't use record such as described in previous posts you can have 2 arrays:
[pascal]BulletX,BulletY: array[0..99] of integer;[/pascal]

[psycho]

Guess who's back!
I'm almost done with the game, I still have to finish the movement for the enemies, their shooting and as always, fix the freaking bugs! I managed to get around the shooting function for the spaceship, and I am pleased to announce that I did not have to use an array or a record for such action. All I did was declare two separate variables containing the x,y coordinates of the ship and then applying them to the 2D array.
Now here's the problem: I can't make the ship shoot and move at the same time, meaning that until you press the space bar, the ship won't move unless the bullet is drawn on the screen... Could it be because I am calling the readkey and keypressed functions from two different procedures? (One to move the ship and the other to shoot).
Here's some of the code, mainly the shooting procedure and the moving one:

procedure crear_bala(variable_dario_x,variable_dario_y:byte;var bala_x,bala_y:byte;var puntaje : integer; var Poder_Disparar : boolean; var matriz : tm_matriz; var punta_a:byte);
Begin

if keypressed then
 begin
 if (not Poder_Disparar) and (readkey = spacebar) then
  
	 	 begin
     Poder_Disparar := true;
     bala_x:=punta_a;
     bala_y:=37; {variable que tomo del proc de dario}
	  end;
  end;

 IF (Poder_Disparar) and (bala_y>1) THEN
  begin
   dec(bala_y);
   if ((matriz[bala_x,bala_y]<>'M') and (matriz[bala_x,bala_y]<>'R')
      and (matriz[bala_x,bala_y]<>'^')) then
    begin
     matriz[bala_x,bala_y] := 'I';
     gotoxy(bala_x,bala_y);
     write(matriz[bala_x,bala_y]);
     if matriz[bala_x,bala_y+1]='I' then
      begin
       matriz[bala_x,bala_y+1]:=' ';
       gotoxy (bala_x,bala_y+1);
       write (matriz[bala_x,bala_y+1]);
      end;
    end;

BTW that's for the bullet, it's in spanish i know... crear_bala = bullet creation poder_disparar = canshoot
And for the movemente:

procedure Mover_Nave(var matriz: tm_matriz; var punta_d, punta_i, punta_a: byte; var tecla:char);
var
    fil, col, i: byte;
begin
    i:=0;
    if (tecla='d') then
        begin
        col:=punta_d;
        for fil:=38 downto 36 do
            begin
            while (matriz[col,fil]='^') do
                begin
                int(matriz[col,fil],matriz[col+1,fil]);
                gotoxy(col+1,fil);
                write(matriz[col+1,fil]);
                gotoxy (col,fil);
                write (matriz[col,fil]);
                dec(col);
                end;
            inc(i);
            col:=punta_d-i;
            end;
        inc(punta_d);
        inc(punta_i);
        inc(punta_a);
        end;
    i:=0;
    if (tecla='a') then
        begin
        col:=punta_i;
        for fil:=38 downto 36 do
            begin
            while (matriz[col,fil]='^') do
                begin
                int(matriz[col,fil],matriz[col-1,fil]);
                gotoxy(col-1,fil);
                write(matriz[col-1,fil]);
                gotoxy (col,fil);
                write (matriz[col,fil]);
                inc(col);
                end;
            inc(i);
            col:=punta_i+i;
            end;
        dec(punta_d);
        dec(punta_i);
        dec(punta_a);
        end;
end;

MAIN LOOP this is where I need help also...

begin
 dis_mars_fil:=6;
 dis_mars_col:=6;
 clrscr;
 perdiste:=false;
 colicion:=false;
 hay_tiro:=false;
 cant_vidas:=3;
 cargar(m_matriz,punta_marcianos_x,punta_marcianos_y);
 mostrar(m_matriz);
 cargar_nave(m_matriz,pd,pi,pa);
 vida (m_matriz);
 gotoxy (1,2);
 write('012345678901234567892123456789312345678941234567895123456789612345678971234567');

 while not perdiste do
  begin
   delay(50);
   resta_vida (colicion,cant_vidas,perdiste,m_matriz);
   p_disparo_marciano (m_matriz,hay_tiro,colicion,punta_marcianos_x,filnav,punta_marcianos_y,colnav,x_bala,y_bala);
		crear_bala(variable_dario_x,variable_dario_y,bala_x,bala_y,puntaje,Poder_Disparar,m_matriz,pa);
   if keypressed then
            begin
            teclapresionada:=readkey;
								mover_nave(m_matriz, pd, pi, pa, teclapresionada);
            end;


  end;
end.

All variables are declared correctly, I just need help with the keypressed and readkey functions. I only posted the code I need help with cause the rest is too long...
Please help me! I need to finish this by Thursday or im screwed! THANK YOU ALL
PS Is it possible to attach a file?

[psycho]

Never mind mates, I got it going
I just embedded the if statement that checks for the spacebar in the ship's movement procedure.
Now to finish off the martians...