Update README.md

Author: mwenge

src/README.md

@@ -1,46 +1,3 @@
 ## Matrix for the VIC 20 and Commodore 64
 
-Matrix was originally written for the Vic 20 in 1983 and later ported to the C64 in 3 days. You can
-read more about each implementation in the notes for each of the ports, but here we collect some observations
-on the differences between the two versions.
-
-### A small bug in the C64 port
-![zapper](https://user-images.githubusercontent.com/58846/109517849-9ac72d80-7aa1-11eb-954d-3b93cf39dd84.gif)
-
-Minter converted the Vic 20 to C64 in a hurry and left at least one small bug behind in the process. The
-original Vic 20 version animates the tail of the 'zappers' as they move across the screen. This is achieved
-by a neat trick which bitshifts one of the bytes that makes up the 8-byte character set definition for the
-'zapper' glyph.
-
-```asm
-;-------------------------------------------------------------------------
-; AnimateZapperTail
-;-------------------------------------------------------------------------
-AnimateZapperTail
-        LDA charsetLocation + $0109
-        ROL 
-        ADC #$00
-        STA charsetLocation + $0109
-        RTS 
-```
-
-When porting to C64 he forgot to update the 'STA' statement to refer to the new location of the character
-set:
-
-```asm
-; AnimateZapperTail
-;-------------------------------------------------------------------------
-AnimateZapperTail
-        LDA charSetLocation + $0109
-        ROL 
-        ADC #$00
-        ;FIXME: should this be charSetLocation + $0109 like in Vic20?
-        STA f1509
-        RTS 
-```
-
-Instead of storing the updated, bit-shifted byte to its original location of $2109, he instead stores it
-to the equivalent location of the byte in the Vic 20 version ($1509). The result is that the animation
-doesn't happen. It's very hard to notice this bug in practice as the characters are much smaller on a C64
-screen and the effect is too subtle in C64 to notice its absence.
-
+To learn more about the source code for Matrix, Gridrunner and other games in the Gridrunner series, checkout [Gridrunner:The Little Black Book](https://github.com/mwenge/llamaSource/blob/main/GridrunnerTheLittleBlackBook.md), a work in progress dissecting the internals of these Llamasoft games.