Lovebyte 2024 Apple II sizecoded Demos

Background

Source Code

Byte-athlon

The Entries

Oldschool 1k -- Don't Tell Valve

A scene from your favorite cake-acquisition simulator! This was a 512 byte entry that got out of hand. This is sort of based on the

Oldschool 1k -- Plasma Mask

I had much grander plans for this, including having it alternate with a hi-res version of the plasma (like in the second reality demo) as they share a lot of the same code/lookup tables. In the end this was the best I could manage.

This is based on the code from the French Touch "Plasmagoria" demo by Grouik. Everything was massively shrunk down and as much as possible generated on the fly.

This includes the 768 bytes of SINE tables. (I actually had to use a FFT to reverse-engineer which values were used for the sines, I've tried for years to get a nice plasma on Apple II and have never managed to do it myself).

To save space the Applesoft (Microsoft) BASIC FAC floating point routines are used to generate the SINE tables, which is *slow*. I'd probably be better off doing some fixed point math but while faster that might take more room.

I ended up compressing the entire program using zx02 compression. This let us have three full-screen masks which compress down to essentially nothing.

Thanks to mA2E for making the music track. To fit in a reasonable (256 bytes or so) space I essentially hand-craft a tracker that is tiny, and also makes some assumptions about having a Mockingboard in Slot #4, left channel audio only.

Optimizing compressed code is a pain, as shaving off bytes often makes everything larger. The final challenge was trying to get the credits printed during the precalc. Spent a lot of time re-arranging the source code so that the full line could be printed.

Finish: 2/7 1k Oldschool
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256B Intro -- Desire Wires

I've had this hi-res wires effect around for a while, for so long that I forget how the vertical line drawing part of it works. It wasn't a convenient power-of-2 size and not really that exciting. I thought maybe I'd combine it with the tiny rectangle-drawing code from the abandoned work on the 1k dtv demo, add some page flipping, and maybe it would make something mildly compelling.

Finish: 17/21 256B Oldschool Intro
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128B Intro -- Rainbow Squares

This is a cool looking pattern that is surprisingly colorful for Apple II hi-res which only has 6 colors. It's two frames from Hellmood's sierpinski rotozoom (in Memories) that I found by accident. For this intro we just (slowly) draw the two frames to PAGE1 and PAGE2 and then page flip them rapidly in a decreasing rate. A speaker click is mixed in to give some sound when drawing.

Finish: 10/19 128B Oldschool Intro
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64B Intro -- Box Entropy

This is based off of a famous Applesoft BASIC 2-liner "entropy" by Dave McKellar. It's hard to replicate the exact effect without floating point, and especially without a good random number generator. I made an approximation of one in 6 bytes using ROM values EORed with another ROM value indexed with the Y value. Still not great but made it slightly less repetitive.

The effect is just using XDRAW to draw boxes of size 1, with randomly increasing it to size 2. That's it, but it makes a neat effect. The realization that helped this time was the BASIC shape tables were actually already double sized, so I could reduce it from 10 to 6 bytes as long as I made the SCALE values 2,4 instead of 1,2.

Finish: 9/16 64B Oldschool Intro
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32B Intro -- Sawblade

More Apple II shape tables. Was trying rotating things around the middle of the screen, which is hard because you waste 9 bytes to get the drawing starting there. Also wanted the scale to be 1 so we start with the *second* byte of the code at $E7 (HGR_SCALE) wasting a bit at $E6 where we start. It's using ROM at $E2E0 as the shape, and increasing the SCALE after each rotation.

Finish: 7/13 32B Oldschool Intro
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CALL -151
E6: A0 01 20 D8 F3 A8 A2 8C  A9 60 20 11 F4 A2 E0 A0
F6: E2 E6 E8 A5 E8 29 3F D0  02 E6 E7 20 5D F6 F0 E5
E6G

32B Intro -- Spiraling Shape

Another shapetable demo, again I was trying for rotating around the center of the screen again (which as mentioned takes 9 bytes). We did get a nice spiral effect. We're using the shape at $E2DF. We load at $E9 so that $FE which we use as rotation happens to be in the right place in the code for loading as a constant. We don't have to set HGR_SIZE at $E7 because we base its value off the rotation. This freed up enough room for the 3 bytes it takes to get a little sound going.

Finish: 1/13 32B Oldschool Intro
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CALL -151
E9: 20 D8 F3 2C 30 C0 A8 A2  8C A9 60 20 11 F4 A2 DF
F9: A0 E2 E6 FE A9 01 29 7F  85 E7 20 5D F6 F0 E4
E9G

16B Intro -- hhhh

Now that 16B is official I didn't want there to not be an Apple II representative. I thought I was out of time but then the deadline was mysteriously increased so I had time to search for yet another interesting (to me at least) XDRAW pattern.

This one did look a bit more compelling in the emulator than it does on the screen capture (all of these were captured on an actual Apple IIe platinum). I thought it looked like some sort of sci-fi spaceship background. The name is from the "hhhh" pattern at the start of the run.

Sadly I wasn't able to wake at 6am to watch the compo live.

Finish: 2/22 16B Oldschool Intro
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CALL -151
E7: 20 D8 F3 20 57 F4 A9 E3 A8 88 AA 20 5D F6 F0 F6
E7G