Metroid 2600 - Released

[Rabbit 2600]

My current project is a hack of Berzerk, I'm trying too make a Metroid game, I really wanted too use Alien, Wizard of Wor or Dark Cavern, but editing the sprites where a bit odd so I resorted to Berzerk instead. This is what I've done so far: Changed the robots into metroids and the player into Samus. I still have to give Evil Otto a makeover. Here's a screenshot, what do you think about the spriting? Good enough?

 

EDIT - The graphical hack is now complete - Look further down for the fixed edition

Edited September 29, 2012 by Rabbit 2600

[PFL]

Is this just a GFX hack or do you have plans for gameplay changes too?

[Pixelboy]

Interesting hack.

 

You could press the game select switch to switch between the ice beam and missiles. You could also collect missiles (simple dots within the mazes) to replenish your limited supply. That would make it really Metroidy.

 

Just my two cents.

[gambler172]

Hi Rabbit

looks cool

greetings Walter

[Rabbit 2600]

For the moment it's just a graphical hack, but I want too learn and make more advanced hacking and change some gameplay elements. My current task is too learn how too change the color of the playfield. Which is really hard and I have no clue how to do it yet =)

[Rabbit 2600]

I discovered a glitch with the Metroid sprite, when they shot down they would kill themselves, I've fixed it now, here is the improved version:

Metroid 2600.bin

[Rabbit 2600]

Made a label:

Edited October 10, 2012 by Rabbit 2600

[PFL]

I don't see the label...

[HatefulGravey]

Neat, I can't wait to give this a shot. I can't even see the screen shots right now because I'm at work, but I love Berzerk and graphic hacks are cool so I'm sure this will be a blast.

[Rabbit 2600]

I fixed the bad link to the lable, should be working now =)

[Atari Adam]

As a Metroid fan from the beginning this is brilliant! great work

[Nukey Shay]

Be aware that there are 2 game-killing errors in the original game (attract mode timer and reserve life addition). Correcting either of them are easy using a disassembly.

 

To fix the first glitch, store the current LSR'ed stick value (in the accumulator) to the attract timer when the stick is moved.

 

Fixing the second needs an additional branch to abort reserve life addition if already at 127 lives. Just use BMI to skip storing if the new value is 128.

[Nukey Shay]

Fix #1:

LF339:
      lda    #$00    ;2
      sta    $E7     ;3
      lda    #$7F    ;2
      sta    $E8     ;3
      lda    SWCHA   ;4
      lsr            ;2
      lsr            ;2
      lsr            ;2
      lsr            ;2
      eor    #$0F    ;2
;;       and    #$0F    ;2 superfluous
;;       bne    LF363   ;2
      bne    LF361   ;2 altered branch

      lda    #$00    ;2
      sta    $91     ;3
      sta    $FD     ;3
      sta    $92     ;3
      lda    $84     ;3
      bne    LF365   ;2
      inc    $87     ;5
      bne    LF365   ;2
      lda    $80     ;3
      jmp    LF21E   ;3
;using the 2 bytes saved above to fix...
LF361:
      sta    $87     ;3 store to attract mode

Edited October 13, 2012 by Nukey Shay

[Nukey Shay]

Fix #2:

LFA21:
      adc.wy $00DD,Y ;4
      sta.wy $00DD,Y ;5
      lda    #$00    ;2
      dey            ;2
      bpl    LFA21   ;2
      cld            ;2

;BIT doesn't affect the accumulator,
;so move the LDA and AND up above it
      lda    $E7     ;3
      and    #$1F    ;2

      bit    $88     ;3
      bvs    LFA3B   ;2
      bpl    LFA4F   ;2
;;       lda    $E7     ;3
;;       and    #$1F    ;2
      cmp    #$19    ;2
      bne    LFA4F   ;2
LFA3B:
;;       lda    $E7     ;3 remove this
      and    #$0F    ;2
      cmp    #$09    ;2
      bne    LFA4F   ;2
      lda    $E7     ;3
      cmp    $DE     ;3
      beq    LFA4F   ;2
      lda    #$03    ;2
      sta    $81     ;3
      inc    $DA     ;5
;use the 4 bytes saved here...
      bpl    LFA4F   ;2 branch if still less than 128
      dec    $DA     ;5 bump lives back down

LFA4F:
LFA72: ;moved label to reuse rts
      rts            ;6

LFA50:
      lda    $E3     ;3
      asl            ;2
      eor    $E3     ;3
      asl            ;2
      asl            ;2
      rol    $E4     ;5
      rol    $E3     ;5
      lda    $E4     ;3
      and    #$7F    ;2
      sta    $E6     ;3
LFA61:
      clc            ;2
      adc    $E7     ;3
      sec            ;2
      cmp    $E8     ;3
      bcc    LFA72   ;2
      beq    LFA72   ;2
      lsr    $E6     ;5
      lda    $E6     ;3
;;       jmp    LFA61   ;3
      bpl    LFA61   ;3 change to unconditional
;;LFA72:
;;       rts            ;6

[Nukey Shay]

BTW editing the sprites in Alien is no problem if you know how the sprite data is arranged. Every other bitpattern line comes from a seperate data table...so you need to alter two data tables for each sprite.

 

For example...

 

This:

       .byte %00010110 ;$16 ; |   X XX | $F454 Alien frame A 1
      .byte %01011101 ;$5D ; | X XXX X| $F455 Alien frame A 3
      .byte %00110000 ;$30 ; |  XX    | $F456 Alien frame A 5
      .byte %01110000 ;$70 ; | XXX    | $F457 Alien frame A 7
      .byte %01111101 ;$7D ; | XXXXX X| $F458 Alien frame A 9
      .byte %10001000 ;$88 ; |X   X   | $F459 Alien frame A 11
      .byte %10000100 ;$84 ; |X    X  | $F45A Alien frame A 13
      .byte %00000000 ;$00 ; |        | $F45B (end of bitmap)

 

...plus this:

       .byte %00011111 ;$1F ; |   XXXXX| $F558 Alien frame A 2
      .byte %01110100 ;$74 ; | XXX X  | $F559 Alien frame A 4
      .byte %00110000 ;$30 ; |  XX    | $F55A Alien frame A 6
      .byte %01110100 ;$74 ; | XXX X  | $F55B Alien frame A 8
      .byte %11011111 ;$DF ; |XX XXXXX| $F55C Alien frame A 10
      .byte %10001100 ;$8C ; |X   XX  | $F55D Alien frame A 12
      .byte %00000000 ;$00 ; |        | $F55E Alien frame A 14
      .byte %00000000 ;$00 ; |        | $F55F (unused)

...produces this:

       .byte %00010110 ;$16 ; |   X XX | $F454 Alien frame A 1
      .byte %00011111 ;$1F ; |   XXXXX| $F558 Alien frame A 2
      .byte %01011101 ;$5D ; | X XXX X| $F455 Alien frame A 3
      .byte %01110100 ;$74 ; | XXX X  | $F559 Alien frame A 4
      .byte %00110000 ;$30 ; |  XX    | $F456 Alien frame A 5
      .byte %00110000 ;$30 ; |  XX    | $F55A Alien frame A 6
      .byte %01110000 ;$70 ; | XXX    | $F457 Alien frame A 7
      .byte %01110100 ;$74 ; | XXX X  | $F55B Alien frame A 8
      .byte %01111101 ;$7D ; | XXXXX X| $F458 Alien frame A 9
      .byte %11011111 ;$DF ; |XX XXXXX| $F55C Alien frame A 10
      .byte %10001000 ;$88 ; |X   X   | $F459 Alien frame A 11
      .byte %10001100 ;$8C ; |X   XX  | $F55D Alien frame A 12
      .byte %10000100 ;$84 ; |X    X  | $F45A Alien frame A 13
      .byte %00000000 ;$00 ; |        | $F55E Alien frame A 14
      .byte %00000000 ;$00 ; |        | $F45B (end of bitmap)
      .byte %00000000 ;$00 ; |        | $F55F (unused)

[Rabbit 2600]

Cool! Thanks for the help!

[Nukey Shay]

Sprite editing in Alien is much easier using a disassembly which has the bitmap data defined up top as labelled constants:

AlienA01 = %00010110
AlienA02 = %00011111
AlienA03 = %01011101
AlienA04 = %01110100

etc. so that in the data tables, they will be seperated for you by using those labels:

 

      .byte AlienA01 ; $F454
     .byte AlienA03 ; $F455
     .byte AlienA05 ; $F456
     .byte AlienA07 ; $F457

etc.

 

Zero values in the first table are used as delimiters (defines where a bitmap image ends)...but zero values in the second table are allowed. Keep this in mind if you need blank lines within a sprite image.

[Rabbit 2600]

I'll look into it once I can get a disassembler working, no luck yet

[YANDMAN]

looks cool, here's my label

 

[Classic Pac]

Very cool