Quackers (August 2nd)

carlsson · Post by **carlsson** » Sun Aug 01, 2004 4:23 pm

For Game of the Week, I had a lot of options (which I may utilize another time), but when browsing my VIC library, this one struck me like the lightning. Thus, I have chosen Quackers by Interesting Software (!) as the Game of the Week.

This game features:

* smooth scrolling, colourful graphics
* terrible sound (!)
* two scenarios of play
* stress factor as time runs out
* runnable on unexpanded VIC-20

Since the original game as found on the FTP sites is PAL only and for no obvious reason archived as a cartridge (good luck finding it?!), I decided to NTSC fix and make it loadable on unexpanded machine:

http://www.mds.mdh.se/~dal95acn/vicfiles/quackers.prg

My high score is 3250 p (set on Saturday using real VIC), which still is 200 points below my brother's score. Grr, but now I have a reason to try to beat it.

And yes, it is Monday since 25 minutes ago local time when this is posted!

Boray · Post by **Boray** » Mon Aug 02, 2004 4:22 am

Hmmm... The version I have is NTSC only.... Is the one at Zimmers PAL?

/Anders

Boray · Post by **Boray** » Mon Aug 02, 2004 4:29 am

Or does your fixed version work on both NTSC and PAL?

/Anders

carlsson · Post by **carlsson** » Mon Aug 02, 2004 4:45 am

The fixed version should run (at least in VICE - I have no NTSC VIC to test it on) on both. The otherwise downloadable version moves the screen to PAL default X/Y, which will put it out of the way in NTSC mode. Maybe you have a third, pure NTSC version?

The fix consists of the following changes:

LDX #$0F changed to LDX #$0D
LDA $1381,X changed to LDA $1383,X
STA $9000,X changed to STA $9002,X

or in other words, the first two bytes in the initialization setup table are not used since they would not change the standard screen position anyway.

Boray · Post by **Boray** » Mon Aug 02, 2004 5:09 am

Great!

The version I have must be NTSC only. It is a file version for the unexpanded vic on a tape from 1982 or 83 probably... I played it some weeks ago when going through some old tapes. I could play it helpfully as I easily can change the x position of the whole screen with a knob on the front side of my Philips 8833-2 monitor. I can then ALMOST see the whole screen...

But a PAL version is of course a lot nicer, thanks!

/Anders

carlsson · Post by **carlsson** » Mon Aug 02, 2004 6:31 am

I noticed that the music sounds much different (judged in VICE) in the two display modes. While I know that the scale is slightly different between NTSC and PAL, it should not be that much different. I wonder if the scale is calculated based on system frequency or something. Maybe your copy plays music much lighter in PAL than this one does, or the emulator does something very strange?

Boray · Post by **Boray** » Mon Aug 02, 2004 7:19 am

Hey!!! How awful that bear blinks!!! I didn't recall that it blinked at all on my tape version, so I tried it again, and how smooth and nice the bear is there!!! I managed to copy it to disk into two files, one for the main memory and one for the tape buffer. Without both it doesn't work. I will try to fix NTSC/PAL the way you did. If I can't manage to do that, then I will send it to you and maybe you can fix it...?

/Anders

vic user · Post by **vic user** » Mon Aug 02, 2004 7:46 am

That's a bear!?

I thought I was shooting at a turtle!

Chris

Boray · Post by **Boray** » Mon Aug 02, 2004 7:54 am

It usually is bears you shoot like that... but maybe this is a turtle

Anyway, I managed to do Carlsson's fix, but guess what? It started to blink just as much as the PAL/fixed version, so I really prefer the NTSC version (on PAL). And here it is:
http://home.worldonline.se/boray/datorm ... rsNTSC.zip

It's 3 parts. I managed to preserve the original loading screen as well (but I had to change it from tape to disk as well as loading one extra part (the tape buffer))...

The blinking is probably because of some raster beam timing. Maybe Carlsson can make a fix for that too? It's blinking a little in the rabbits as well...

/Anders

Post by **Jeff-20** » Mon Aug 02, 2004 10:21 am

This is one of my TOP 5 Vic 20 games!

I was so excited when I played it for the first time. I have never been able to get a hold of the cart; however, I downloaded a copy of the ftp and copied it to disk. The game is a perfect answer to Carnival for Colecovision.

The most impressive feature, to me, is the programming doesn't make any effort to disguise being a Vic 20 game. It is very loyal to the native VIC graphics and feel.

The company name and copyrights at the top of the screen are VERY vic-20ish. It has the look and feel of a type-in or tape program. The rabbit graphic was done better in Compute's Bunny Hop. The graphics actually are not very good, but they scroll! Remember how much cache the word "scroll" once had?

The game actually is quite strange without knowledge of the Carnival arcade game. It doesn't even make sense! The bottom row is aliens, the top is smiley faces.

This is probably the most influential game in my own programming efforts. The intermission and other small features are comparable to my humble basic program Robot Riot (which you can get in the basic section).

I can't wait to play this again! I will post a high score once I find the disk.

carlsson · Post by **carlsson** » Mon Aug 02, 2004 10:32 am

I have now found out why the game flickers in PAL. It uses the raster counter ($9004) to determine on which rows it should do update:

Raster $29 (dec 41): NTSC top of row 5 (countdown timer), PAL bottom of row 1 (title)

Raster $49 (dec 73): NTSC bottom of row 12 (white rabbits), PAL top of row 9 (just below the black moving bars)

Raster $51 (dec 81): NTSC bottom of row 14 (black aliens), PAL top of row 11 (just below the blue ducks)

By changing the raster values to the corresponding rows on PAL ($29 = $36 (dec 54), $49 = $56 (dec 86), $51 = $5e (dec 94)), I got rid of the flicker. Preferrably I would find a set of raster rows which are OK for both PAL and NTSC, but I'm unsure where to find them.

carlsson · Post by **carlsson** » Mon Aug 02, 2004 11:09 am

Since I have nothing better to do (not quite true), I finally fixed the timing so it will run on either video mode. To fit it into memory, I had to Pucrunch the file, so it actually loads shorter than before:

http://www.mds.mdh.se/~dal95acn/vicfiles/quackers.prg

Technical explanation: I replaced the occurences of absolute raster lines with references to zero-page addresses $B8, $B9, $BA which I preload with the most suitable ones based on the content of $9000 (X-position). This means the file is somewhat different than before, but I think the impact on timing and gameplay is about non-existing.

Boray · Post by **Boray** » Mon Aug 02, 2004 11:49 am

Unknowing of Carlssons efforts, I also fixed the problem... But I did something else (a lot simpler

). I just moved the screen to y position 25 which is the NTSC default and voila! I used Carlsson's fixed version plus the original loader/starting screen. This version should also be playable on both PAL and NTSC... Here it is:
http://home.worldonline.se/boray/datorm ... ackers.zip

/Anders

carlsson · Post by **carlsson** » Mon Aug 02, 2004 12:31 pm

Feh. I never figured that would work. Besides, that is almost as far up as my 14" TV can display a picture.

Let's say you cured the symptom and I cured the cause?

Boray · Post by **Boray** » Tue Aug 03, 2004 5:11 am

I like this game! It's fun and looks nice even on my worst vic chip. Nice with the extra bear/turtle part so that you don't get tired of the game that fast. And now we have two PAL versions that is better than the original PAL cartridge!!! Hehehe!

.... Are you ready for my high-score? You better sit down: 10630 points. I got it when playing it once this morning...

/Anders