Random Map Pitfall!

[vdub_bobby]

Here's a Pitfall! with a randomly generated map. Well, it starts off with the same one every time, but hit (and hold for a fun tour, ) RESET to change to a new random map. I increased the starting time so that you have more time to explore.

 

Thoughts?

 

EDIT: The map probably isn't random, just your starting location. See here:

http://www.atariage.com/forums/index.php?s...ndpost&p=927514

RandomPitfall_.bin

Edited September 8, 2005 by vdub_bobby

[vdub_bobby]

New version, no noticeable changes; just cleaned up some code a little.

RandomPitfall_.bin

[supercat]

Here's a Pitfall! with a randomly generated map.  Well, it starts off with the same one every time, but hit (and hold for a fun tour, ) RESET to change to a new random map.  I increased the starting time so that you have more time to explore.

 

Thoughts?

926343[/snapback]

 

It might be nice to include "Freecell-style" randomness, where you allow the player to select a random speed. This would allow people to e.g. hold a contest for who can get the best score within a week on game #4921.

[vdub_bobby]

Here's a Pitfall! with a randomly generated map.  Well, it starts off with the same one every time, but hit (and hold for a fun tour, ) RESET to change to a new random map.  I increased the starting time so that you have more time to explore.

 

Thoughts?

926343[/snapback]

 

It might be nice to include "Freecell-style" randomness, where you allow the player to select a random speed. This would allow people to e.g. hold a contest for who can get the best score within a week on game #4921.

927071[/snapback]

Yeah...I thought about that. Couple reasons why I didn't, and probably won't, code that in:

1. It would require a lot more code, and probably require making the binary 8K. A lot of work.

2. The way the random number generator works in Pitfall! means that *I think* that, no matter the initial random seed, the map is always the same - you just start at a different point in it. And what's so cool about that? Once you figure out where you are starting, you can run through the game basically the same way you would for regular Pitfall!, just starting at a different point.

[Crimefighter]

Reading this post, I had thought this game had generated a randomized gamemap entirely instead of moving your starting position in random locations.

[vdub_bobby]

Reading this post, I had thought this game had generated a randomized gamemap entirely instead of moving your starting position in random locations.

927647[/snapback]

So did I, at first.

[+FujiSkunk]

Reading this post, I had thought this game had generated a randomized gamemap entirely instead of moving your starting position in random locations.

927647[/snapback]

So did I, at first.

927667[/snapback]

 

So it isn't a new, randomly generated map? If not, you might want to tweak your first post and/or the thread title.

 

Edit: Unless this is the September 8th version of an April Fool's joke, in which case I aplogize for not getting it.

Edited September 8, 2005 by skunkworx

[+batari]

Here's a Pitfall! with a randomly generated map.  Well, it starts off with the same one every time, but hit (and hold for a fun tour, ) RESET to change to a new random map.  I increased the starting time so that you have more time to explore.

 

Thoughts?

926343[/snapback]

 

It might be nice to include "Freecell-style" randomness, where you allow the player to select a random speed. This would allow people to e.g. hold a contest for who can get the best score within a week on game #4921.

927071[/snapback]

Yeah...I thought about that. Couple reasons why I didn't, and probably won't, code that in:

1. It would require a lot more code, and probably require making the binary 8K. A lot of work.

2. The way the random number generator works in Pitfall! means that *I think* that, no matter the initial random seed, the map is always the same - you just start at a different point in it. And what's so cool about that? Once you figure out where you are starting, you can run through the game basically the same way you would for regular Pitfall!, just starting at a different point.

927514[/snapback]

In that case, I assume the random number generator is 8-bit. I'd see about making it 16-bit, which I think would only require a few bytes of ROM and one byte of RAM.

[+batari]

In that case, I assume the random number generator is 8-bit.  I'd see about making it 16-bit, which I think would only require a few bytes of ROM and one byte of RAM.

927722[/snapback]

Looking at source, I found that the LFSR in the game is much more complex than it needs to be, which could save lots of space:

.loopRandom:
; random' = random >> 1 | (bit4^bit5^bit6^bit1) * $80
   lda    random          ; 3
   asl                    ; 2
   eor    random          ; 3
   asl                    ; 2
   eor    random          ; 3
   asl                    ; 2
   asl                    ; 2
   rol                    ; 2
   eor    random          ; 3
   lsr                    ; 2
   ror    random          ; 5
   dex                    ; 2
   bpl    .loopRandom     ; 2³

The above is for movement to the left. For movement to the right, it does this:

.loopRandom:
; random' = random << 1 | (bit3^bit4^bit5^bit7)
   lda    random          ; 3
   asl                    ; 2
   eor    random          ; 3
   asl                    ; 2
   eor    random          ; 3
   asl                    ; 2
   asl                    ; 2
   eor    random          ; 3
   asl                    ; 2
   rol    random          ; 5
   dex                    ; 2
   bpl    .loopRandom     ; 2³

 

The LFSR I have been using is as simple as this, and probably works just as well:

 lda random
 lsr
 bcc noeor
 eor #$B2 
noeor
 sta random

 

Making the above 16-bit would actually save space.

 

Note that Pitfall's LFSR is reversible. However, making mine reversible is not too hard if you use this in place of the other one.

 lda random
 asl
 bcc noeor2
 eor #$65 
noeor2
 sta random

 

Then there's room to play with to add another byte and make a 16-bit LFSR... Hopefully.

[vdub_bobby]

Then there's room to play with to add another byte and make a 16-bit LFSR... Hopefully.

927779[/snapback]

I don't know much about pseudo-random number generators (LFSR) - if you give me a 16-bit reversible LFSR I'll try to put it into Pitfall!

 

There is a fair amount of space (and free RAM) if you remove the screen saver code.

[+batari]

I don't know much about pseudo-random number generators (LFSR) - if you give me a 16-bit reversible LFSR I'll try to put it into Pitfall!

Try this - I think it will work. Replace the LeftRandom and RightRandom subs with these. You also need to define random_hibit to be equal to an unused byte in memory.

LeftRandom SUBROUTINE
; generate new random scene on the left:
 lda random
 lsr random_hibit
 ror
 bcc noeor
 eor #$B2 
 tax
 lda random_hibit
 eor #$A0
 sta random_hibit
 txa
noeor
 sta random

 

RightRandom SUBROUTINE
; generate new random scene on the right:
 lda random_hibit
 asl random
 rol
 bcc noeor2
 eor #$41
 tax
 lda random
 eor #$65
 sta random
 txa
noeor2
 sta random_hibit
 jmp ContRandom

 

EDIT: Oh yeah, there are four locations in the code where there is "lda random" and these need to all be modified to this:

 lda random
 eor random_hibit

Don't do a global search and replace though, as the "lda random2" doesn't need changing, and you don't want to change the code you just replaced with the above.

Edited September 9, 2005 by batari

[supercat]

In that case, I assume the random number generator is 8-bit.  I'd see about making it 16-bit, which I think would only require a few bytes of ROM and one byte of RAM.

927722[/snapback]

 

Going with a 16-bit LFSR makes the game have a set of 65536 rooms (or whatever the period is) rather than 256, but the game will always play the same for any position within the set. Because of the larger set of rooms, there's no realistic way to traverse all of them within a reasonable time.

 

If the goal is to ensure that all 256 of the original rooms appear once within a 256-room map, there are two other approaches that may work better:

 

-1- Keep the room number as a byte 0-255. When going into a room, put that number through a mapping function to convert it into the room contents.

 

-2- Apply a reversible transformation before and after doing the room-to-room movement. For starters, assuming the original routines are called "left" and "right" and there's stack space (and time) to call them, I would suggest the following:

newleft:
 jsr left
 lda room
 clc
 adc seed
 sta room
 jsr left
 lda room
 sec
 sbc seed
 sta room
 jmp right

newright:
 jsr right
 lda room
 clc
 adc seed
 sta room
 jsr right
 lda room
 clc
 adc seed
 sta room
 jmp left

 

I don't know whether the sequences generated by the above will be interesting, but they should all be 256 rooms long and visit all of the original rooms, though (except for seed #0, corresponding to the original game) they will be in different sequences.