Sr. Developer @easytechgreen

Week of the 04/05/2020 - #19



  • Intereting developer: Max Strauch
  • More Important Apple II resources
  • Demoscene - Some other cool demos
  • GNU Rocket OpenGL editor
  • Applesoft BASIC Quick Reference
  • Jupyter notebook for Apple II palette
  • Pouet logos
  • Macinstosh Emulators
  • 51 Byte Parallax Scrollbar Apple II demo

Intereting developer: Max Strauch

His site seems very interesting and neat. Should look into it: [web]. I came to his page because he created a hardware emulated Apple II with an Atme AVR microcontroller. He did his batcherlos thesis which you can download from the site as well. You can watch the machine running here: [YouTube]

Apple II Emulation on an AVR Microcontroller

More Important Apple II Resources

  • About Apple II Technical Notes - This page has all Apple II related technical notes converted to HTML [web]. There is vey thorough description of Double High-Resolution Graphics on one of the notes [web]

Demoscene - Some other cool demos

  • Megademica 4K - 4k ZX Spectrum Revision 2019 Winner. [Pouet] [YouTube]
  • Brainwave - Revision 2019 - Compo - PC 64K Intro. [YouTube]. There’s also a “making of” in [YouTube]

Brainwave 1 Brainwave 2 Brainwave 3 Brainwave 4

  • Collection of best BbcMicro demos - What people create in one tweet of code for a 1980s computer [YouTube]. Twitter account where you can see daily submissions. [Twitter].
  • Second Reality - This is a classic from the 90’s by Future Crew. [YouTube] [GitHub]
  • Scroll Scroll Scroll - Another very cool Apple II demo by FRENCH TOUCH VAULT. [web]
  • cellular automata visualization test - Not really a demo but pretty cool. [YouTube]. There’s a Shadertoy version which doesn’t work too good for me (takes a little while to start) [Shadertoy]

Celluar automata visualization test 1 Celluar automata visualization test 2 Celluar automata visualization test 3

GNU Rocket OpenGL editor

This is an OpenGL editor used by XY the coder of the Brainwave 64K demo. [GitHub]

Applesoft BASIC Quick Reference

  • Applesoft BASIC in JavaScript - [web]
  • Very nice reference of Applesoft BASIC - [web]

Jupyter notebook for Apple II palette

I wrote a little snippet of Jupyter code to plot the Apple II palette:

import matplotlib.pyplot as plt
import numpy as np

palette = [
    [  0,  0,  0],[227, 30, 96],[ 96, 78,189],[255, 68,253],
    [  0,163, 96],[156,156,156],[ 20,207,253],[208,195,255],
    [ 96,114,  3],[255,106, 60],[156,156,156],[255,160,208],
    [208,221,141],[ 20,245, 60],[114,255,208],[255,255,255]

rgb = []
numColors = 16
for color in range(0, numColors):
    rgb_pixel = palette[ color ]

rgb_m = np.array(rgb)
rgb_m.shape = (4, 4, 3)

plt.imshow(rgb_m, interpolation='none',origin='upper' )

Apple II palette

Pouet logos

Pouet, the demo scene site is running (always?) a contest to choose logo. Here are a couple of the ones I liked the most

logo 1 logo 3

Macinstosh Emulators

The awesome ‘Devine Lu Linvega’ (one half of Hundred Rabbits) has been playing with Hypercard and Pascal on a Macintosh so it got me interested on Mac emulations. Here are a couple of resources:

51 Byte Parallax Scrollbar Apple II demo

This week I worked on an idea for an effect on an Apple II. The seed came from watching this YouTube video of a collection of tiny BBCMicro demos [YouTube] and the Brainwave 64k Demo entry from Revision ‘19 [YouTube]. In particular this small section:

Brainwave 3

That part of the demo shows some scrolling bars with different speed and parallax. I wanted to get an idea of how fast the Apple 2 could render graphics using assembler in low res mode. I started with vertical bars (no way I’ll attempt to do it diagonal!) and just a single row. I was interested in vertical since on the Apple 2 it makes for thinner bars. I tweaked a little bit and got it down to 175 bytes (I’m sure I can lower that number from my later experience but for the moment I might come back to this later). This is the result:

Bruna - 175 bytes

After that I wanted to try to do this effect (or similiar) with as few bytes as possible. After making lots of tweaks I managed to get it down to 51 bytes. This is how it looks:

Bruno - 51 bytes

Finally to add some variations I created a third version which cycles through 4 colors. Here it is running:

Bruni - 62 bytes

I also uploaded a YouTube video with all them running here. Here’s the source for the 62 byte version. You can see all the project on my Apple II development Github project [GitHub]

!cpu 6502

           *= $a0 ; ORG = $A0

; =====================================
PTRFG               = $a1       ; reuse beginning of code
PTRBG               = $9f

            jsr $f832           ; clear screen
            sta $C050           ; Lowres gfx
            bmi .start          ; skip from 128-255
            bne +

            dec+1 PTRFG
            inc+1 PTRBG
            bne .blit

            lda (PTRFG),y
            bcc +
            lda #$ff
            bne .blit
+           lda (PTRBG),y
            and #%00000001
            beq .blit
            and #%00000011
            lda+1 COLORS,x
            sta $500,y
            sta $580,y
            sta $600,y
            sta $680,y

            lda #$8
            jsr $fca8

            bcs .start

COLORS  !byte $33,$11,$bb,$55