PoP versions where the slow-fall potion changes the screen's colors

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David
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PoP versions where the slow-fall potion changes the screen's colors

Post by David »

I found out that in some versions of PoP the slow-fall potion on level 7 changes the screen's colors while its effect lasts.

PC98: https://www.youtube.com/watch?v=qz6yYVLXqnI&t=4m11s

PC Engine: https://www.youtube.com/watch?v=_TgPsgo77F8&t=26m54s

Atari ST: https://www.youtube.com/watch?v=Qrxk_VaSm6E&t=16m34s

FM Towns: https://youtu.be/tsOkGEf0eko?t=1611
[By the way, it seems this video is by the same person who wrote this article: viewtopic.php?p=19511#p19511 ]

As a related note, in the SNES version the potion changes only the prince's colors: https://youtu.be/aZtkPZih-3s?t=3328
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Re: PoP versions where the slow-fall potion changes the screen's colors

Post by David »

It happens in the Apple II version as well.
slow_fall_colors.png

What's strange is that this is not seen in the only video I found about level 7 of PoP Apple II.
https://youtu.be/JZDAPp61aak?t=1694

Maybe the emulator used in the video didn't support the method used by the game for changing the colors.
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Re: PoP versions where the slow-fall potion changes the screen's colors

Post by dmitrys »

I wonder why they did not implement it in the DOS version of PoP. Maybe versions 1.0-1.1 did not easily support custom palettes for dungeons.

I have done a "drinking entrance" in my mod that changes a level palette in SDLPoP after drinking a potion in a dark room.
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Re: PoP versions where the slow-fall potion changes the screen's colors

Post by David »

David wrote: December 31st, 2020, 2:31 pm What's strange is that this is not seen in the only video I found about level 7 of PoP Apple II.
https://youtu.be/JZDAPp61aak?t=1694
There is a comment below the video pointing this out:
thepirategamerboy12 wrote: Interesting, I was playing this game on real hardware earlier and at 28:16 it's supposed to wildly shift the colors even on the OG version, yet this doesn't happen at all in emulation it seems.
I found another Apple II video, but it doesn't show this discoloration either: https://youtu.be/JMc7cBVwF-k?t=212
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Re: PoP versions where the slow-fall potion changes the screen's colors

Post by Osiride »

It looks like it does happen on the AppleWin emulator: https://youtu.be/embxlnm5r2w?t=1930. It's odd that an emulator wouldn't support it, but it's possible, I suppose.
Do you guys know if the Apple II game had different revisions like the DOS port? Maybe the effect was added later?
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Re: PoP versions where the slow-fall potion changes the screen's colors

Post by Norbert »

Osiride wrote: April 16th, 2022, 11:16 pmDo you guys know if the Apple II game had different revisions like the DOS port? Maybe the effect was added later?
As I understand it, at the very least it originally had separate releases on 3.5" and 5.25" floppy disks. (Some one-sided and some two-sided?) Additionally, there are recent releases (re)build from the source code, that include various modifications, such as enabling cheats, cracking copyright protection, etc. All the disk images that I know of can be found in a ZIP file I've attached to this post. This includes disk images in various formats, namely .2mg and .po (both single-disk) and .nib and .woz (both double-disk), and .dsk (up to three disks, including boot).

On top of all that, emulators impact gameplay, as you wrote.
This includes their customizable settings, such as which exact Apple II model to emulate (II, II+, IIe, IIc, IIGS).

I may give various disk images a try in various emulators to see which combinations change the screen colors...
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Re: PoP versions where the slow-fall potion changes the screen's colors

Post by tacosalad »

Osiride wrote: April 16th, 2022, 11:16 pm It looks like it does happen on the AppleWin emulator: https://youtu.be/embxlnm5r2w?t=1930. It's odd that an emulator wouldn't support it, but it's possible, I suppose.
Do you guys know if the Apple II game had different revisions like the DOS port? Maybe the effect was added later?
Ooo, lucky timing! Not only do I know how the color-change was achieved...I just happen to have an Apple II set up today so I can demonstrate it!

The color-change effect was present in the original Apple II version (not added later) but it exploits an unintended/undocumented feature of the video hardware: the AN3 switch.

History: The earliest Apple computers could display only 40 columns of text, but with the Apple //e revision A they added an 80COL switch (IO ports $C00C and $C00D) which could double the amount of text being displayed. Starting with the Apple //e revision B the AN3 switch (IO ports $C05E AND $C05F) could extend the 80COL feature to the graphics modes to double the number of pixels. There's an undocumented combination of these switches that suppresses the blue and orange colors, instead turning them into purple and green.

Here's a practical demonstration on my Apple II. After starting a game, I pressed the reset button twice to interrupt it and used keyboard commands to show these graphics that were still in the computer's memory.
PoP graphics as they would normally appear
PoP graphics as they would normally appear
Then I selected the undocumented combination of 80COL and AN3 switches via the IO ports and the Prince of Persia graphics changed from blue and orange to green and purple.
PoP graphics with undocumented combination of 80COL and AN3
PoP graphics with undocumented combination of 80COL and AN3
This behavior was retained in subsequent Apple II models (AFAIK) but probably omitted from some emulators because Apple's documentation of it was totally unintelligible! Here's the relevant excerpt from page 58 of Apple's Extended 80-Column Text/AppleColor Adaptor Card Manual. What the heck was this table supposed to mean??
Awful documentation
Awful documentation
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Re: PoP versions where the slow-fall potion changes the screen's colors

Post by Osiride »

tacosalad wrote: May 17th, 2022, 4:34 am
Osiride wrote: April 16th, 2022, 11:16 pm It looks like it does happen on the AppleWin emulator: https://youtu.be/embxlnm5r2w?t=1930. It's odd that an emulator wouldn't support it, but it's possible, I suppose.
Do you guys know if the Apple II game had different revisions like the DOS port? Maybe the effect was added later?
Ooo, lucky timing! Not only do I know how the color-change was achieved...I just happen to have an Apple II set up today so I can demonstrate it!
I couldn't wish for a better answer, thank you for the insight!
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Re: PoP versions where the slow-fall potion changes the screen's colors

Post by tacosalad »

Norbert wrote: April 17th, 2022, 11:34 am On top of all that, emulators impact gameplay, as you wrote.
This includes their customizable settings, such as which exact Apple II model to emulate (II, II+, IIe, IIc, IIGS).

I may give various disk images a try in various emulators to see which combinations change the screen colors...
Here's a BASIC program you can use to test whether a particular Apple II (or Apple II emulator) supports that color-switching feature. Just type this program into Applesoft BASIC and type RUN. (Be sure to proofread the numbers used in those POKE statements!)

The program draws horizontal stripes in all 6 of the Apple II's default colors: black, green, purple, orange, blue, and white. Press 1 and 2 to toggle the 80COL/AN3 switches and watch the screen:
  • On an older Apple II+ or Apple //e Revision A, the switches won't have any effect. It will show all 6 colors regardless of whether you press 1 or 2.
  • On an Apple //e Revision B or Apple //c, pressing 1 will cause the orange and blue stripes to turn green and purple, so there are only 4 colors. Pressing 2 will show all 6 colors again.
  • On an Apple //gs I don't know what it will do. This is an undocumented feature, so it might not be supported.

Code: Select all

10 HGR
20 FOR A = 10 TO 79
30 HCOLOR= A / 10
40 HPLOT 0,A TO 279,A
50 NEXT A
60 PRINT "PRESS 1 OR 2 TO SWITCH COLORS"
70 GET A
80 IF A=1 THEN POKE 49164,0: POKE 49246,0: PRINT "80COL OFF, AN3 OFF"
90 IF A=2 THEN POKE 49164,0: POKE 49247,0: PRINT "80COL OFF, AN3 ON"
100 GOTO 70
This should accurately predict whether the slow-fall potion will affect the screen colors.
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