Blade Runner - another broken game! Bug needing a fix :(

[Xyphoe]

Hi guys!

It seems I'm not having much luck recently with doing longplays and bugged games! 

This time I'm looking at Blade Runner.

It's pretty simple stuff - you've got to shoot 24 'replicants' (move you ship over the map, press fire over a flashing icon (replicant) to land and shoot them - switches to side-scrolling shoot-em-up where you run along and shoot the guy (replicant) that's running away from you avoiding pedestrians and other ships/cars)

The game basically crashes or rather resets to the title screen around the 11th to 13th replicant.
On shooting him one time the game freezes until you press a key - the ship starts it ascent and the game resets to the title screen!!  ARGGH! 

I have a snapshot you can load in WinApe attached - it's for the tape version 64k
http://cpc-power.com/index.php?page=detail&onglet=dsk&num=406
http://cpc-power.com/pages/download.php?fiche=406&dsk=9

If you need any more info or explanation let me know. I took a look in WinApe debugger for text and messages (which you can find from 0280 to 0560), it appears you can complete the game because I see the text "The End" there (I guess there's no ending screen then!)

I hope that someone can work out the cause of this bug and fix it. I've tried other dumps of the game and same/similar thing.

[Xyphoe]

Has anyone taken a look at this at all?

[Puresox]

The crapness of the game may have scared them off? . Although I do hope someone does take a look , I am missing your Lp's.

[Gryzor]

I had never seen the game, but it doesn't look that bad. And it looks surprisingly Blade Runner-ish, too! Too bad I can't understand what to do and how to control it...

[ivarf]

I remember the good music in this game.    I never go very far in the game, but still enjoyed it. Several years later I watched the excellent film and was totally stunned

[Xyphoe]

It's probably not helped matters for those that downloaded the SNAP having to work out what the hell is going on, and fighting against a really hard opponent who very easily kills you (he's one the highest rating replicants and lethal!). Maybe I would have been better doing a vid to show it.

Well I'll leave it a couple more days I think to see if anyone comes in with a fix and will do the longplay anyway noting it's bugged and crashes (by that point you've seen all the game has to offer anyway I suppose!)

[genesis8]

I wrote a message about your problem on http://cpcrulez.fr/forum/viewtopic.php?f=6&t=4868

Where they already did patch some problematic games.

[Xyphoe]

Thank you, that's very kind of you.

I may hold off for a bit then and maybe do a quick vid of it in action to help illustrate - you have to run off and shoot the man running *away* from you (everyone else moving towards you are pedestrians) - at this level it's quite hard to shoot him without practice as he very easily kills you.

[genesis8]

Solution by Hermol, webmaster of CPCRulez : 3 NOP starting at &AA6 to avoid coming back to the main menu after the ship goes away from the street.

[Xyphoe]

Solution by Hermol, webmaster of CPCRulez : 3 NOP starting at &AA6 to avoid coming back to the main menu after the ship goes away from the street.

Cool, not quite sure what I need to do exactly in WinApe debugger window ... could someone less thick as me elaborate and explain? Sorry 

[Nich]

Cool, not quite sure what I need to do exactly in WinApe debugger window ... could someone less thick as me elaborate and explain? Sorry 

You need to select the "Debug" option from the menu, then select "Pause" - or alternatively, just press the F7 key. This will open the WinAPE Debugger window. Click on the bottom window with the list of hexadecimal bytes.

Near the bottom right of the window is a pointing hand. Click on this, or press Ctrl+G, and a window should appear asking for an address to go to. Enter 0AA6. The byte at address 0AA6 should now be highlighted, and the sequence of bytes at this address should be "C2 CF 07". Enter 00 00 00 to overwrite these bytes (00 represents the NOP instruction on a Z80).

Please note that I have not actually played the game so I don't know if Hermol's suggestion works!

[Xyphoe]

You need to select the "Debug" option from the menu, then select "Pause" - or alternatively, just press the F7 key. This will open the WinAPE Debugger window. Click on the bottom window with the list of hexadecimal bytes.

Near the bottom right of the window is a pointing hand. Click on this, or press Ctrl+G, and a window should appear asking for an address to go to. Enter 0AA6. The byte at address 0AA6 should now be highlighted, and the sequence of bytes at this address should be "C2 CF 07". Enter 00 00 00 to overwrite these bytes (00 represents the NOP instruction on a Z80).

Please note that I have not actually played the game so I don't know if Hermol's suggestion works!

Ahhh thanks Nich, really I knew all the above but what I should have been more specific about was what "NOP" stood for and what to do ... ie enter 00's, but that totally confused me and made me thing I should be doing something completely different.


OK! That kinda worked!
The bug happened, but it went back to the map screen but the replicant wasn't dead, but I was able to select him to fight and I could then kill him, looks like it cleared the bug! I kept going to replicant 24 which should be the last one.....

1) With the NOPs in place, weirdly the game carried on and put 4 new replicants to kill 
2) Without (ie the original values back in place) after successfully killing  him without bug happening, I ascended in my ship and it went back to the title screen. Meh. Bug or expected ending to the game?....

However if you look at around 02B4 you will see the text "THE END" ... perhaps this is the message that should flash up when completing the game? Could someone ask Hermol to see what triggers this message and what jumps to it perhaps?

Nearly there!!!

[Johnny Olsen]

Hi Xyphoe

you are only allowed to hit 5 pedestrains.
The problem is that when you hit one of the harder replikants (2 or 3 hit to die) you also hit a Pedestrian.

After you hit a hard replikant the code jump from &19a7 to &19c9 and there sub one Pedestrian

Try poke &19a8,&19 maybe it solves the problem.

You can use your "bladerunner_64ktape_test_13.sna" file to test just poke &19a8,&19 and poke &19cc,x  x=Pedestrian hit default 6

The freeze thing is not a bug - the game wait for a keypress in &3239

I can't find the replikants counter (24 replikants or 6 rounds) maybe you have to kill 36 replikants 36=&24 hex.

When you reach 500.000 point you will see the very nice end screen.


198b: ld hl,(&1911)
198e: inc l
198f: ld a,(hl)
1991: inc l
1991: cp &06
1993: ld a,&82
1995: jr nz,&19ca


1997: ld de,&02f2    ---    pointer to the word "Hit"
199a: ld (&0287),de
199e: add a
199f: add a
19a0: push af
19a1: ld a,&03       ---    Hit counter (Replikants) - could be 1,2 or 3
19a3: dec a          ---    Sub one hit
19a4: (&19a2),a      ---    save new hit counter
19a7: jr nz,&19c9    ---    if not zero then jump to &19c9 - Try change to jump to &19c2 (&19a8,&19)

19a9: ld de,&02fa
19ac: ld (&0287),de
19b0: ld a,&c9
19b2: ld (&1bf5),a
19b5: ld a,&fe
19b7: ld (&2040),a
19ba: ld (&1c47),a
19bd: ld a,&af
19bf: ld (&17e4),a

19c2: ld a,(&19cc) 
19c5: inc a          ---    add one hit (Pedestrian)
19c6: ld (&19cc),a


19c9: pop af
19ca: ld (hl),a
19cb: ld a,&05       ---    Hit Counter (Pedestrians)
19cd: dec a          ---    Sub one hit
19ce: ld (&19cc),a   ---    save new hit counter
19d1: srl a
19d3: jp z,&1aac     ---    If Zero the jump to dead
19d6: ld hl,&03f8    ---    else pointer to the message "Warning Pedistricide is an ....."
19d9: dec a
19da: jr z,&19e2



By the way - try poke &1dc,5 when you play the map part

[Xyphoe]

Hi Johnny,

WOW! Thank you sir for taking the time to look into this and present your findings, that's really appreciated!

I believe we have found at least a work-around for this issue and the cause of it.

Yes it does appear that the 'pedestrian hit' counter is at the root of this and the game subs a pedestrian when hitting this replicant. I think this is a bug somehow, because I've tested when no pedestrian was in the 'line of fie' in front of the replicant to the best I can, it always happens.

Poke &19A8,&19 does appear to work

Also increasing poke &19CC value (ie pedestrian hit counter) does work too.
In the attached .sna that value is really low at 02, and it appears the game stops for killing pedestrians when it's at 01, so if I increase that value I can continue on fine and problem solved!

So well done and I can always rely on you now it seems to fix and find bugs/solutions! 

I still think somewhere there's a bug, because otherwise the pedestrian hit counter would have got very low very quickly! Also...

> The freeze thing is not a bug - the game wait for a keypress in &3239

There's no other point in the game where it does require a keypress.

If you shoot pedestrians and too many of them - you get the appropriate message appear in the text window. On 'my bug' the text window isn't scrolling any text at all which is really odd.

[Xyphoe]

When you reach 500.000 point you will see the very nice end screen.
.
.
.
By the way - try poke &1dc,5 when you play the map part

COOL! So there is an ending, and you have to get to 500,000 points! I see that poke tells the map screen that the number of value per 100,000 points, so poking 5 means 500,000 right?
And voila... ending screen!

Sheesh though... that's an awful lot of points to get. I tested until replicant number 32 and I was on 300,000-ish points
To make matters worse there's a set number of scientists, which are slowly being killed off. So it's a kind of global time limit. At this point in the game there's only 1 scientist left, so it's pretty much impossible to complete anyway. Certainly with 1 shot kills and game over!!! GRRR!

[Carnivius]

Never played this before but gave it a go cos I like the movie.  It's not a bad little game.  Didn't take long to figure out what was what and I got quite into it.  Helped partially by the rhythm of the music too.   And a strange sense of satisfaction of shooting those replicants in the back. 

[Johnny Olsen]

COOL! So there is an ending, and you have to get to 500,000 points! I see that poke tells the map screen that the number of value per 100,000 points, so poking 5 means 500,000 right?

yes

I tested until replicant number 32 and I was on 300,000-ish points

Maybe there's another way to reach the end screen.
I still think you have to kill 36 replicant's - &24 hex is the way computer's count's which is equal to 36 dec - perhaps an error in the manual

If you poke &19a2,01 you only have to hit the replicant's one time - it would make the game much easier.

Please can i have a snap file with 32 replicant's killed?

[Xyphoe]

Maybe there's another way to reach the end screen.
I still think you have to kill 36 replicant's - &24 hex is the way computer's count's which is equal to 36 dec - perhaps an error in the manual

Well! After an evening testing (or wasted? Why do I put myself through this and waste my time! lol!) and a lot of snapshot reloading I got all the way up to replicant number 48!!!!!!

After I killed him my score then ticked over the 500,000 mark... which is when I got the ending screen.

Hmmph.

Where did you see the "&24 hex" thing and think this might be a counter for the ending?

[Xyphoe]

Sorry to necro an old topic, but I've done a huge amount of more work into this game, as has Johnny Olsen again for me.

We've both reached the point where we can do no more. And I'll be live streaming this evening (10pm on YouTube) the game trying to beat with a few things we've implemented and poked.

The game is still very broken and bug ridden. Attached is a text file with all that is wrong, what can be fixed, and what we haven't been able to fix. Any hope of sorting out all the problems I don't think will happen, eg the scientists bug where at the start of a new wave the counter for them doesn't reset back to 4 if some were killed in a previous wave so less spawn, making the game near impossible to beat - Johnny couldn't find this counter and looks like there's a fair bit of self modifying code there too.

Basically it's a mess! See the attached file, and feel free to tune in at 10pm (BST) this evening on YouTube to see me discuss, play and hopefully 'beat' it! https://gaming.youtube.com/c/Xyphoe/live

[Sykobee (Briggsy)]

I wonder if the game writers were planning a difficulty selector screen and then ran out of time, and shipped it with the most difficult settings.


E.g., Easy - 1 hit replicants, 10 pedestrians allowed to be killed, 200,000 / 24 to win
Medium - 2 hit replicants, 8 pedestrians allowed to be killed, 300,000 / 36 to win
Hard - 3 hit replicants, 5 pedestrians allowed to be killed, 500,000 / 48 to win


I wonder if someone can make a CPR with the possible bug fixes and a trainer / difficulty selector.

[Gryzor]

Thanks for the update man! Sadly that will be too late for me to watch, hope I catch it tomorrow!

[dragon]

Sorry to necro an old topic, but I've done a huge amount of more work into this game, as has Johnny Olsen again for me.

We've both reached the point where we can do no more. And I'll be live streaming this evening (10pm on YouTube) the game trying to beat with a few things we've implemented and poked.

The game is still very broken and bug ridden. Attached is a text file with all that is wrong, what can be fixed, and what we haven't been able to fix. Any hope of sorting out all the problems I don't think will happen, eg the scientists bug where at the start of a new wave the counter for them doesn't reset back to 4 if some were killed in a previous wave so less spawn, making the game near impossible to beat - Johnny couldn't find this counter and looks like there's a fair bit of self modifying code there too.

Basically it's a mess! See the attached file, and feel free to tune in at 10pm (BST) this evening on YouTube to see me discuss, play and hopefully 'beat' it! https://gaming.youtube.com/c/Xyphoe/live

Have you play the spectrum version, it appears a port of it, the spectrum have the bugs?.

O.k then the scientific are located in &007c/0083 The are 16 bytes for each, each 8 byte are x coordinate and y coordinate, when a scientific dead the x coodinated are changed to FF-> so ff= dead.

[arnoldemu]

007c is referenced 7 times in the code.


c15, 1164, 11f3, 143e, 146e, 14b4, 1500

c01 appears to generate a random position. so this looks to be initialising.
it also checks at c1a if the value is ff or not.

14da, 14db,14dc, take that out and they should not die.

[dragon]

There are other  indirect checks.

in &116f  when is reading the x coordinate the ff causes  the activation of jump so ff is write back in the same place. This happend at change of level.

inc a ff=0 z flag activated. &116a read x coordinate.

if i have a dead scientific,i add the patch at fly ,he continue dead, because the old ff is here. but eilminating the inc a causes rare effects. without your parch the first scientific is dead now, because i alter the obscure table is reading all time in &0054/55 &005e/f 0068/69  &0072/73 in &14d1/14d7 With you patch apply and eliminating inc a i cause a reset.

Change only 1170/1/2 to 00 appears works, but is strange. It appears is made deliberatery, not a bug really.

This is a dsk  with the two  patches (bug 1+2) to test.

About the other bug, the starpoint is put a breakpoint in memory write in &0AA4. this variable change the valor indicated if the game need load star menu, map etc..  So when bug #3 appear and stop in the breakpoint make a snapshot. From now i can't reproduce it lucky question.

[Xyphoe]

Have you play the spectrum version, it appears a port of it, the spectrum have the bugs?.

O.k then the scientific are located in &007c/0083 The are 16 bytes for each, each 8 byte are x coordinate and y coordinate, when a scientific dead the x coodinated are changed to FF-> so ff= dead.

WELL FOUND!

I think it also solves the random 'game over' I experienced.

I had 1 scientist left, and took a snapshot after I was ascending up after killing a replicant, the map screen loads, then the map screen sort of refreshes itself... then game over occurred.

After the map refreshes the values all changed apart from the ones with FF load. So it's on this reload, it detected that 4 replicants have been killed and it's the end of the wave - thus respawn 4 new replicants and any remaining scientists to new locations.

The values starting from &007C were ->

FF 21
0B 26
FF 21
FF 21

At this point before it could find the game over and kick me, I changed the first one from "FF 21" to "0B 21" .... I didn't get a game over!

So I allowed 1 or 2 seconds to wait and see if the game over kicked in, it didn't. And rechecking the code the 2nd scientist that was alive was NOT anymore - he had changed from "0B 26" to "FF 26".

How he had died... I do not know. I think he had respawned, but on top of a replicant which is an instant kill.