Nukey?

[neotokeo2001]

Need some help if you have the time. I am looking for the background color location for Vanguard and Alien. Also is there any way to speed up the control of the ship in Vanguard. It seems to move half the speed it should.

[Nukey Shay]

The background color is saved at 2 points in Alien...though in the disassembly, only 1 point can be located by searching for COLUBK: the bonus round...when the foreground and background are both zeroed - BTW the maze is still there

 

LFD55:
      LDA    $80                    ;3
      AND    #$20                   ;2
      BEQ    LFD8D                  ;2
      LDA    #$00                   ;2 black background during bonus stage
      STA    COLUBK                 ;3

 

 

To locate the other point, I just traced the SWCHB equate. In Alien, the colors will be changed to monochrome when B&W is selected (the way that it does this is by using an AND value to strip away bits IF B&W is selected)...

       TXS                           ;2 start with %11111111
      LDA    SWCHB                  ;4
      AND    #$08                   ;2 check B&W
      BNE    LF766                  ;2 if color, skip next line
      LDX    #$0D                   ;2 use %00001101 instead
LF766:
      TXA                           ;2 move that bit pattern to A
      LDY    #$00                   ;2
      BIT    $80                    ;3
      BVC    LF773                  ;2
      LDY    $BF                    ;3
      ORA    #$02                   ;2
      AND    #$F6                   ;2
LF773:
      STA    $9E                    ;3 save the bit pattern to $9E
      STY    $84                    ;3
      LDA    $E8                    ;3
      BNE    LF78F                  ;2
      LDX    #$08                   ;2
LF77D:
      LDA    LFE3C,X                ;4 get value from a table
      EOR    $84                    ;3
      AND    $9E                    ;3 strip away bits when B&W
      STA    $F5,X                  ;4
      CPX    #$07                   ;2
      BCC    LF78C                  ;2
      STA    VBLANK,X               ;4 when X = 7 or 8, save to the color registers

 

So all that really needs changing is the last 2 bytes in table LFE3C...

 

LFE3C:
      .byte $BE; |X XXXXX | $FE3C
      .byte $1E; |   XXXX | $FE3D
      .byte $5E; | X XXXX | $FE3E
      .byte $8E; |X   XXX | $FE3F
      .byte $4E; | X  XXX | $FE40
      .byte $1E; |   XXXX | $FE41
      .byte $8E; |X   XXX | $FE42
      .byte $60; | XX     | $FE43 wall color in maze section
      .byte $84; |X    X  | $FE44 screen color in maze section

 

 

 

VERY rough disassembly + cfg...

Alien.zip

[Nukey Shay]

BTW by trimming out a few bytes in the program area, the table at the end can be moved (so that the game is playable on an unmodded Supercharger).

Alien_Supercharger_.zip

[Nukey Shay]

I'm not clear on what you had in mind for Vanguard (because making the player's ship faster would make the game too easy IMO)...but here's a rough disassembly of that game:

Vanguard.zip

[Nukey Shay]

Quicker ship:

Fast_Vanguard.zip

[neotokeo2001]

Quicker ship:

847091[/snapback]

 

That is exactly what I was looking for. Thanks again Nukey.