Super Mario Bros. - 128 Lives Fix

[Jorpho]

Well, it's easy enough to do accidentally if you're doing one of the extra life tricks like in 3-1.

Anyway, yes, there is now a thread at RH.net.

[drunk3nj3sus]

Well, it's easy enough to do accidentally if you're doing one of the extra life tricks like in 3-1.

Anyway, yes, there is now a thread at RH.net.

Yeah I can see how it could be done but I don't really think anybody would need more than 20 or so lives to beat the game, if you're going to the trouble of hacking that bug out of the game you might as well just disable the lives system altogether. Only bug I've ever really disliked in the game is the one where you can accidentally get stuck in blocks.

[ColecoFan1981]

Sorry to re-open this thread, but now I've figured it out.

In Super Mario All-Stars, this was how it got fixed:

CheckLives:
    INC NumberofLives ;increment the lives counter by one
    LDA NumberofLives ;then reload it to see if player has 128 lives
    CMP #$80             
    BCC WereGood      ;if not past 128 lives yet, we're good
    LDA #$7F             
    STA NumberofLives ;otherwise, set A=128 lives
WereGood:
    RTL               ;end of routine

Another way to do this:

CheckLives:
    INC NumberofLives ;increment the lives counter by one
    LDA NumberofLives ;then reload it to see if we have more than 128 lives
    BPL WereGood      ;if not past 128 lives yet, we're good
    DEC NumberofLives ;otherwise decrement counter by one to prevent overflow
WereGood:
    RTL              ;end of routine

~Ben (ColecoFan1981)

[SparTonberry]

Why would you LDA and INC the number of lives in that second example? It's pointless.

[ColecoFan1981]

Why would you LDA and INC the number of lives in that second example? It's pointless.

The same would apply to the first example, too... I too would like to know why not to INC right after LDA? It might be because INC is like LDA #$01+STA.

A better way to do this would be:

CheckLives:
    lda NumberofLives ;load the lives counter
    cmp #$7f          ;check if player has 127 lives
    bcs EndCheckL     ;skip to end of routine if so
    inc NumberofLives ;otherwise increment counter by one
EndCheckL:
    rtl

Saves a lot of bytes.

Another way...

CheckLives:
    lda NumberofLives ;load the lives counter
    bmi EndCheckL     ;skip to end if negative flag set
    inc NumberofLives ;otherwise increment counter by one
EndCheckL:
    rtl

~Ben

[ColecoFan1981]

Why would you LDA and INC the number of lives in that second example? It's pointless.

OK, I fixed the examples I listed. In SMAS, the lives counter is incremented first, and then reloaded to see if the target result has been met.

~Ben