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ROM Hacking Discussion / Pokemon Red priority move altering

« on: May 10, 2012, 04:39:00 am »

I'm trying to work on a hack of Pokemon Red, and this aspect is proving to be a bit of a challenge for me. In Gen I, the only high priority move was Quick Attack. What I'd like to do is alter the check so that more moves are recognized as priority moves, but this is a bit of an issue. The code at $3C2E5 is where the check for Quick Attack takes place, as translated by DASMX (the comments are mine):

Code: [Select]

3C2E5 : FA DC CC "   " ld a,(X1D1D)  ; load value from (CCDCh) to accumulator, which is the byte used to indicate your selected move
3C2E8 : FE 62 " b" cp 01DH       ; compare to 62h, which is the indicator for the move Quick Attack
3C2EA : 20 0A "  " jr nz,LC2F2   ; jump if not equal to LC2F2
3C2EC : FA DD CC "   " ld a,(X1717)  ; (CCDDh) is the byte that indicates your foe's selected move (for a CPU trainer, this value is set immediately once you select your move)
3C2EF : FE 62 " b" cp 007H       ; once again, compare with 62h
3C2F1 : 28 21 "(!" jr z,LC30A    ; jump if equal to LC30A
3C2F3 : C3 7D 43 " }C" jp L1207      ; jump to L1207
If I change the "62" into "21", I can make it so that Tackle is the high priority move rather than Quick Attack. That's all fine and good, but if I want to have it check another move by inserting code "FE 21 20 0A" at $3C2EC and removing some blank data at the end of the bank so the ROM doesn't exceed $FFFFF in size, battles will always fail to load and you will be unable to move after speaking with a trainer.

Could the issue with this be the fact that adding in this code messes up jump addresses, and is there any way I can alleviate this issue other than going through the entire bank and modifying every jump address, which will no doubt be a pain in the butt? I was thinking I could put a "jump to" that leads to an area in the middle of the blank data where I can have all the necessary compares and whatnot, then another jump that leads back to the original code, flooding any unused bytes with NOPs so that the offsets don't actually change.

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Newcomer's Board / A few questions regarding the SMB3 timer

« on: October 26, 2011, 05:52:41 pm »

I want to try my hand at creating a Pit of 100 Trials style hack for Super Mario Bros. 3, and the timer is proving to be a bit problematic. While I could just take the lazy route and give the player unlimited time to clear all the segments, I'd like to have that little extra bit of pressure that the clock brings.

I'd like start the timer with 200 seconds and have some pickups scattered around (preferably the Mushroom/Flower/Star goal card pieces that you can add in as pickups) that can add bonus time. Is there any quick way to edit these sprites so that they add bonus time as opposed to giving Mario a goal card, or would it involve a lot of assembly modification? In addition, is it possible to change the initial timer of 200 seconds to something different like 100 or 999?

The goal card sprites I'm talking about are sprites 0x21, 0x22 and 0x23, known as "Flashing Mushroom/Flower/Star" in SMB3 Workshop.
November 01, 2011, 08:18:43 pm - (Auto Merged - Double Posts are not allowed before 7 days.)Nevermind, I figured it out. This can be locked now.

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Newcomer's Board / Re: Introduction Topic

« on: October 15, 2011, 05:51:01 pm »

Hi! I'm ElBlocko, and I've been playing around with Super Mario Bros. 3 and a few other games, mainly Mega Man 3, editing levels, text and such. I'd like to try and get into more serious ROM hacking, though.

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ROM Hacking Discussion / Re: Hack ideas: for those without the skill but with all the ideas.

« on: October 15, 2011, 05:47:27 pm »

Hey everyone. I've got some level editing experience under my belt, but now I'd like to try something a little more advanced regarding Super Mario Bros. 3. Here's the general outline of what I'd like to do:

Like in Paper Mario 2/Super Paper Mario, I'd like to have a Pit of 100 Trials style hack where Mario has to wade through a level that's composed of 100 individual segments, each separated by a pipe or door. I'd like to use one of two formats regarding the timer:

    * A timer that resets whenever you enter a pipe/door, so you've got either 10, 20 or 30 seconds to clear each room before you die of time-up.
    * You start out with 999 seconds in the first segment, and you keep the same timer until the end. If I go this route, I'd also like to see if I can program certain pickups to add bonus time as 999 seconds to clear 100 rooms won't be enough (you'd need to spend an average of 10 seconds per room).

Both these routes would require me to actually hack the game's code, and I'm unfortunately not the greatest hex editor around.