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River Raid Ending?


zaxxonfan

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The first River Raid freezes as soon as you reach one million. And NO, you never get back to the beginning of the river. Nothing ever repeats and there are no tanks. :)

 

On River Raid II, the score ends at 999,999, but you can continue to play as long as you have extra planes left to use. You never earn any more bonus planes since the score is frozen.

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One time I let an emulated hack of River Raid, where the plane was invisible (so couldn't get hit by anything) and had infinite fuel run over night. The next day the emulator was showing all kinds of odd stuff...all the basic elements of the game, but in impossible configurations, ships and copters on the land rather than the water, etc.

 

Since then I've always wondered at one point the river goes nuts...

 

B. Watson came up with a scheme to make screen captures of the "River of No Return", you can see some of the results at http://kisrael.com/viewblog.cgi?date=2005.11.28 ...it's just the early levels, but I think the idea could be easily extended.

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The answer to "At what point..." would probably be "none", because you would have to score above a minimal point value just to reach that point in a legitimate game (where the number generator fails)...and once you get a million, the game dies.

 

BTW Thomas' disassembly at The Dig allows you to enable "trainer" mode...which does the same thing without altering sprites. Keep in mind that you'll need to reset the read address in some of those MiniDig files before you assemble them. Add this to the top of the assembly:

TIA_BASE_READ_ADDRESS = $30

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The answer to "At what point..." would probably be "none", because you would have to score above a minimal point value just to reach that point in a legitimate game (where the number generator fails)...and once you get a million, the game dies.

 

BTW Thomas' disassembly at The Dig allows you to enable "trainer" mode...which does the same thing without altering sprites. Keep in mind that you'll need to reset the read address in some of those MiniDig files before you assemble them. Add this to the top of the assembly:

TIA_BASE_READ_ADDRESS = $30

Well, the answer isn't QUITE none...playing legitmately, the game will freeze before the generation is exhausted, fine, but standalone, then, you should be able to figure out at what point the generation fails , and what exactly goes on when it does.

 

I wonder if they got luck with the pseudo-random seem early, if they tweaked the engine, or if they tried lots and lots of seeds 'til they found a good one...(and I wonder if they ever built a tool to summarize what would be generated for a given number without having to have a human try playing it.)

 

It's such a cool system. I wonder what other 2600 games have that kind of generation going on...some of the maze games obviously use "new" random numbers, but I can't think of anything that has the elegance o River Raid

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How many points are there for shooting a bridge?

Those are the only "must-shoot" targets, theoretically.

 

Because of this, the theshold where the "river goes nuts" may never be reachable at all, if the number of levels to get there times the number of points per bridge > 999,999 points.

 

Regards,

-John

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which begs the question, would it be possible to create a river raid that lets u enter ur own seed or choose a random seed for a different river every time? Also, with the way atari games were full of options, one wonders why it wasn't done in the first place... did hero have similarly created levels, I wonder?

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which begs the question, would it be possible to create a river raid that lets u enter ur own seed or choose a random seed for a different river every time? and with the atari games were full of options, one wonders why it wasn't done in the first place... did hero have similarly created levels, I wonder?

 

Why a random generator was implemented in the first place is because space in a rom cartridge is limited...it was the easiest way to insure that the game levels would be the same from game-to-game (without all of them mapped out in memory). Why it wasn't possible to override this function is obvious...there'd be no way to gaurantee that a seed value could be discovered which allowed very easy gameplay...or which featured very difficult gameplay. So Activision's own 15,000 pt. benchmark and !!!!!! goal would become irrelivant.

 

Dunno about H.E.R.O., but Pitfall! created it's map layout based on a random generator.

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How many points are there for shooting a bridge?

Those are the only "must-shoot" targets, theoretically.

 

Because of this, the theshold where the "river goes nuts" may never be reachable at all, if the number of levels to get there times the number of points per bridge > 999,999 points.

 

 

2000 levels (i.e. bridges). Though due to the narrow passageways on many levels, it would be much sooner than this.

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which begs the question, would it be possible to create a river raid that lets u enter ur own seed or choose a random seed for a different river every time? Also, with the way atari games were full of options, one wonders why it wasn't done in the first place... did hero have similarly created levels, I wonder?

Yes, and Thomas pointed out what byte to change in the disassembly to show a different river each time. It would be trivial to make this value different every time the cart was booted up (seed with INTIM) but Nukey pointed out why Activision didn't do this.

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Huh!

 

How many bytes is that?

 

it would be an interesting hack to rig up an interface to let the user joystick in their own seed, and people could compare seeds and how well they do on them....either a straightforward hex entry (like you were entering initials in an arcade game) or something cuter, like a MegaMan 2 password entry. Dunno if you could do that in the original ROM size or not.

 

Heh, or combine this with some of the work B, Watson was doing, and make graphics of all the different rivers...

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The first River Raid freezes as soon as you reach one million. And NO, you never get back to the beginning of the river. Nothing ever repeats and there are no tanks. :)

 

On River Raid II, the score ends at 999,999, but you can continue to play as long as you have extra planes left to use. You never earn any more bonus planes since the score is frozen.

Thanks for the info.

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; initial values for the random number generator:
SEED_LO		 = $14		 ; change "to go, where no one has gone before" :)
SEED_HI		 = $A8

 

So obviously there is a fixed number of possible configurations available by changing the seed. How many? (My first guess is 256 but I don't know all of the factors involved.)

 

There was another thread on this topic about 3-4 years ago, if someone cares to dredge it up...

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So obviously there is a fixed number of possible configurations available by changing the seed. How many? (My first guess is 256 but I don't know all of the factors involved.)

No, there are 2^16-1 = 65535 values possible (0, 0 is not allowed). 57337 of those will jump somewhere into the sequence of the original River Raid (being 57337 sections long), the others create a different, shorter sequence.

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So obviously there is a fixed number of possible configurations available by changing the seed. How many? (My first guess is 256 but I don't know all of the factors involved.)

No, there are 2^16-1 = 65535 values possible (0, 0 is not allowed). 57337 of those will jump somewhere into the sequence of the original River Raid (being 57337 sections long), the others create a different, shorter sequence.

Ah, I should have known it would be that (256 ^ 2).

 

So I guess this answers the questions others have had then... is it at level 57338 that the game goes haywire?

 

Also, it's interesting to learn that there is really just one fixed sequence of levels, and it's just a matter of which one you're starting in. (I suppose that makes sense, since it's a pseudo-random number generator.)

 

Any other River Raid mysteries you'd care to illuminate? :)

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