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fuzzball: update code comments

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This commit is contained in:
Vince Weaver 2022-02-13 19:11:52 -05:00
parent 3cc0290c89
commit e1e32ea297
1 changed files with 19 additions and 8 deletions
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27
demos/lovebyte2022/fuzzball_32/fuzzball.s
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@ -19,6 +19,10 @@ XDRAW0 = $F65D
.zeropage
; we load at address $E7 in memory, which is the location
; of HGR_SCALE. This means the scale is the first byte of
; the program which is $20 from the JSR
tiny_tiny:
jsr HGR2 ; Hi-res graphics, no text at bottom
@ -28,21 +32,28 @@ tiny_tiny:
sty HGR_SCALE
tiny_loop:
; move back to center of screen
ldy #0 ; Y always 0
ldx #140
lda #96
jsr HPOSN ; X= (y,x) Y=(a)
; move back to center of screen (screen is 280x192)
ldy #0 ; upper byte always 0
ldx #140 ; X-coord
lda #96 ; Y-coord
jsr HPOSN ; X-coord = (y,x) Y-coord =(a)
bit SPEAKER ; click the speaker
rot_smc:
lda #0 ; ROT=0
lda #0 ; ROT=0 (rotation value)
tay ; ldy #>shape_table
; X is 140 here
; The shape table is at memory address (Y,X)
jsr XDRAW0 ; XDRAW 1 AT X,Y
; The effect was found when the original code was modified to not
; have ROT not be 0, and so instead of pointing to the desired
; shape table in the zero page it was walking all across memory
; X is 140 here, since we are pointing at random data it doesn't
; really matter what it is
jsr XDRAW0 ; XDRAW 1 AT X-coord,Y-coord
; Both A and X are 0 at exit
inc rot_smc+1