1K Gymnopedies

aeb · Post by **aeb** » Sun Apr 23, 2006 4:40 pm

Here's my VIC 20 (unexpanded) entry 'Gymnopedies' to Minigame Competition 2006:
http://www.cncd.fi/aeeben/download/gymnopedies.zip

Shoot the pedies until they reach you. Keep the screen clean of rocks or the pedies will get you faster. Watch out for drops that appear when you crush rocks.

Difficulty increases over time and the real game starts when you're around 10000 points.

Joystick is required. Left/right to move, hold button for rapid fire.

Some cheats:

poke4419,165 (immortality)
poke4360,1 (super-fast autofire)

poke5116,89 (star with 9 lives)
poke4867,255 (unlimited lives)

Have fun!

My older VIC 20 entries for Minigame Compos 2003-2004 are found here (Vuokatti, Tammerfors, Whack):
http://www.cncd.fi/download.zip

Minigame Competition page (1K series deadline is 10th May 2006, 4K and 8K later this year):
http://www.ffd2.com/minigame

Cheers,
Aleksi

Schlowski · Post by **Schlowski** » Sun Apr 23, 2006 5:02 pm

mmh, link does not work - but I went to the official page and downloaded it there...
Found it as

Game Name : Realms of Quest II - Special Edition
...
Shoot the pedies ...

So title wrong but description ok

But beside these little problems I'm REALLY impressed by this game - fast, smooth play and especially the bottom (status) line looks great!

Björg

Post by **Jeff-20** » Mon Apr 24, 2006 11:29 am

1k ?! Wow! How do you make the multicolor numbers at5 the bottom? That's not the VIC hi-res multi-color mode.

Schlowski · Post by **Schlowski** » Mon Apr 24, 2006 2:21 pm

Didn't look into the source, but I could imagine foreground color change every scanline???

This was at least my first idea when I saw that and it looks soooo cool!

Björg

Post by **Jeff-20** » Tue Apr 25, 2006 12:48 am

Schlowski wrote:. . .but I could imagine foreground color change every scanline???

But I still don't get it. Can you give me a more detailed description or a code example?

Boray · Post by **Boray** » Tue Apr 25, 2006 2:11 am

There is a beam (the raster beam) that very rapidly paints the whole picture on the TV screen. If you change the background color equally fast in machine language, then you can make it look like there are several background colors at once. There is a register in the vic chip that tells you were this beam currently is painting, so you can time your color changes to this register.

For the game I guess he has made the characters inverted (or made use of the inverted mode) and so to say make the background color the forground color and then changed the background color as I described above.

/Anders

carlsson · Post by **carlsson** » Tue Apr 25, 2006 10:12 am

If you want to change background colour (easier than changing foreground colour for each character), try something like this:

http://www.cbm.sfks.se/files/cbars-ntsc.prg
http://www.cbm.sfks.se/files/cbars-pal.prg
http://www.cbm.sfks.se/files/cbars.a65 (source)

POKE 4247,X to add more delay (larger colour bars) to the loop. It could be done in a much more elegant fashion though.

It was tested only through emulation though, but I'm quite sure it should be stable on a real VIC too.

Post by **Jeff-20** » Tue Apr 25, 2006 7:20 pm

I've seen the technique used in later Atari 2600 games (centipede, california games, etc.) Very interesting!

carlsson · Post by **carlsson** » Wed Apr 26, 2006 5:22 am

The difference is that on the 2600, I believe you have to sync everything with the raster beam for a decent, non-trivial display. On the VIC, you can output characters to the video matrix as you wish and sync with the beam mainly for special effects.

Schlowski · Post by **Schlowski** » Tue May 02, 2006 2:15 pm

The 2600 has no video memory at all, you have to calculate and prepare each and every scanline (read: dots and colors) with raw processor power, this is 76 cycles on each scanline at the NTSC version. And in these 76 cycles you have to switch player, missile and ball graphics on and off for each line you want them to show and construct the so-called playfield, which is the background graphic.
And only when the beam is off, i.e. vertical blank time, you can make your calculations for player movement, AI and game logic... Which is something more than 2000 cycles per frame.

As I learned this I was very, very impressed of what the programmers had pulled out of the machine! In this regard the VIC is a very high tech and sophisticated machine, which is easy to program - at least compared to the 2600

Björg

carlsson · Post by **carlsson** » Tue May 02, 2006 5:22 pm

Ayep, beginners to 6502 are often told that VIC or even more C64 is a great platform to learn the machine code, and once you know it, you can move over to learn the 2600 specialities. Or as I recently wrote on another forum; if programming in machine code (on VIC-20) is about keeping your tongue straight in your mouth, programming on Atari 2600 to me seems like keeping your tongue straight in a mouth full of bits of glass.

Tepic · Post by **Tepic** » Wed May 03, 2006 6:08 am

I'm very damn impressed. In 1k? Geeze, I wish I could do that!

Alan · Post by **Alan** » Wed May 03, 2006 8:58 pm

Looks great in VICE, but it seems to be PAL only, right? I haven't tried it yet on my real NTSC VIC, but it only seems to work with PAL emulation in VICE.

Great job though, I'm real impressed.

aeb · Post by **aeb** » Thu May 04, 2006 5:45 am

Alan wrote:Looks great in VICE, but it seems to be PAL only, right? I haven't tried it yet on my real NTSC VIC, but it only seems to work with PAL emulation in VICE.

Great job though, I'm real impressed.

Yes, it's PAL only. Here's a quick NTSC fix - this should work, at least it works in VICE. There's little flicker at the bottom of screen due to different raster timing (should add some nops there):

poke4439,121
poke4441,206
poke4453,130
poke5106,1
poke5107,1

If you get a garbled screen you could try poke5106,0 too. If that doesn't help then the game screen is just too wide for NTSC.