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xmas2019: update snow

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This commit is contained in:
Vince Weaver 2019-12-20 00:14:04 -05:00
parent e8851b3174
commit b87f6bd166
1 changed files with 106 additions and 59 deletions
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165
xmas_2019/snow.s
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@ -15,6 +15,7 @@ SEEDH = $4F
HGR_COLOR = $E4
SNOWX = $F0
TEMPY = $F1
HGR = $F3E2
@ -31,6 +32,28 @@ NUMFLAKES = 10
jsr HGR
bit FULLGR
;==================================
; init snow
;==================================
ldx #NUMFLAKES-1
snow_init_loop:
jsr random16
lda SEEDL
and #$3f
sta snow_x,X
lda SEEDH
and #$7f
sta snow_y,X
dex
bpl snow_init_loop
display_loop:
; 0 4 8 c 10 14 18 1c
@ -38,35 +61,47 @@ display_loop:
;=========================
; erase old snow
;=========================
; 2 + (35+29+7)*NUMFLAKES - 1
; 1 +71*NUMFLAKES = 711
ldx #0
ldx #0 ; 2
erase_loop:
lda snow_y,X ; get Y
lsr
lsr
lsr ; divide by 8
tay
lda snow_y,X ; get Y ; 4+
lsr ; 2
lsr ; 2
lsr ; divide by 8 ; 2
sta TEMPY ; 3
lda snow_x,X ; 4+
tay ; 2
lda div_7_q,Y ; 4+
ldy TEMPY ; 3
clc ; 2
adc hgr_offsets_l,Y ; 4+
sta GBASL ; 3
;=============
; 35
clc
lda hgr_offsets_l,Y
adc snow_x,X
sta GBASL ; point GBASL to right location
lda snow_y,X ; 4+
asl ; 2
asl ; 2
and #$1f ; 2
clc ; 2
adc hgr_offsets_h,Y ; 4
sta GBASH ; 3
lda #0 ; 2
tay ; 2
sta (GBASL),Y ; 6
;============
; 29
lda snow_y,X
asl
asl
and #$1f
clc
adc hgr_offsets_h,Y
sta GBASH
inx ; 2
cpx #NUMFLAKES ; 2
bne erase_loop ; 3
;============
; 7
ldy #0
lda #0
sta (GBASL),Y
inx
cpx #NUMFLAKES
bne erase_loop
; -1
;==========================
; move snow
@ -97,11 +132,11 @@ just_inc:
jmp snow_no
snow_right:
inc snow_offset,X
inc snow_x,X
jmp snow_no
snow_left:
dec snow_offset,X
dec snow_x,X
snow_no:
done_inc:
@ -112,35 +147,54 @@ done_inc:
;=========================
; draw new snow
;=========================
; 2+ (35+22+19+7)*NUMFLAKES -1
; 1+83*NUMFLAKES = 831
ldx #0
ldx #0 ; 2
draw_loop:
lda snow_y,X
lsr
lsr
lsr
tay
clc
lda hgr_offsets_l,Y
adc snow_x,X
sta GBASL
lda snow_y,X ; 4+
lsr ; 2
lsr ; 2
lsr ; 2
sta TEMPY ; 3
lda snow_x,X ; 4+
tay ; 2
lda div_7_q,Y ; 4+
ldy TEMPY ; 3
clc ; 2
adc hgr_offsets_l,Y ; 4+
sta GBASL ; 3
;===========
; 35
lda snow_y,X
asl
asl
and #$1f
clc
adc hgr_offsets_h,Y
sta GBASH
lda snow_y,X ; 4+
asl ; 2
asl ; 2
and #$1f ; 2
clc ; 2
adc hgr_offsets_h,Y ; 4+
sta GBASH ; 3
;=============
; 19
ldy #0
lda #1
sta (GBASL),Y
ldy snow_x,X ; 4+
lda div_7_r,Y ; 4+
tay ; 2
lda pixel_lookup,Y ; 4+
inx
cpx #NUMFLAKES
bne draw_loop
ldy #0 ; 2
sta (GBASL),Y ; 6
;=============
; 22
inx ; 2
cpx #NUMFLAKES ; 2
bne draw_loop ; 3
;=============
; 7
; -1
lda #100
jsr WAIT
@ -148,10 +202,7 @@ draw_loop:
snow_x:
.byte 2,4,6,8,10,12,14,16,18,20
snow_offset:
.byte 0,1,2,3,4,5,6,7,0,1
.byte 0,0,0,0,0,0,0,0,0,0
snow_y:
.byte 0,0,0,0,0,0,0,0,0,0
@ -191,11 +242,7 @@ div_7_r:
.byte 0,1,2,3,4,5,6 ; 56..62
.byte 0 ; 63
pixel_lookup:
.byte $01,$02,$04,$08,$10,$20,$40
.include "random16.s"