CoordStar

Author: Zirias
Category: Christmas Challenge
System:   C64
Language: Assembler, cc65/ca65 syntax
Len source code: 1146
Len exe file:    78
Len code only:   64
Instructions:

To run the .prg, simply load it and type RUN.

To autostart it with vice:
  x64sc coordstar.prg

To build from source yourself (needs cc65 installed), run
  cl65 -t none -o coordstar.prg coordstar.s

Description:

The star, calculated from its coordinates.

Y (rows) and X (cols) run from -8 to 8 for symmetry. To represent negative
numbers, one's complement is used. This shortens the code to get the absolute
coordinate value, but requires added code to skip the "positive zero" (after
the "negative zero" $FF was already handled). For a few more details, see the
comments in the source file.

Comments:

I started late (on 24th). Yes, that's my excuse :)