r/atari8bit • u/clintp • 8d ago
First Atari program written in 40 years! (details in thread)
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u/These_Brush_6857 3d ago
¡Que bien! ¿Cómo se puede desarrollar un juego que no sea en ensamblador?. Asombroso 👏
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u/SaintLewisMusic73 8d ago
I'm pretty sure others have been written during that time because I've purchased them.
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u/theking4mayor 6d ago
First written by you in 40 years? Because people make Atari programs all the time
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u/clintp 8d ago edited 8d ago
I got the Altirra emulator going and had to do something with it.
This runs on Altirra BASIC (for the
BGETcommand only) otherwise it would be ATARI BASIC compatible. I did this rather than POKE'ing stuff into memory. The ASM and the Katakana characters took FOREVER toPOKE, andXIOis unreliable!There's a smattering of small assembler routines. Page 6 stuff for copying memory blocks, flipping bytes left-to-right, and a memory set routine; a VBI handler to cascade the 4-PM characters down the screen; then a fade routine to decrement the fade table cells, darken the characters as needed, and finally remove the characters from the screen and the fade table.
A BASIC loop does most of the work. It drops text characters behind the PM characters, updates a fade table with the age of the cell, finally copies a random character from the custom character set into the PM shape buffer area. At the end, calls the fade assembler routine above. (There's a little timing problem with the VBI moving the falling characters as BASIC is updating the PM shape, but that just make it look cool.)