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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 HGR_COLOR = $E4
SNOWX = $F0 SNOWX = $F0
TEMPY = $F1
HGR = $F3E2 HGR = $F3E2
@@ -31,6 +32,28 @@ NUMFLAKES = 10
jsr HGR jsr HGR
bit FULLGR 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: display_loop:
; 0 4 8 c 10 14 18 1c ; 0 4 8 c 10 14 18 1c
@@ -38,35 +61,47 @@ display_loop:
;========================= ;=========================
; erase old snow ; erase old snow
;=========================
; 2 + (35+29+7)*NUMFLAKES - 1
; 1 +71*NUMFLAKES = 711
ldx #0 ldx #0 ; 2
erase_loop: erase_loop:
lda snow_y,X ; get Y lda snow_y,X ; get Y ; 4+
lsr lsr ; 2
lsr lsr ; 2
lsr ; divide by 8 lsr ; divide by 8 ; 2
tay 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 snow_y,X ; 4+
lda hgr_offsets_l,Y asl ; 2
adc snow_x,X asl ; 2
sta GBASL ; point GBASL to right location 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 inx ; 2
asl cpx #NUMFLAKES ; 2
asl bne erase_loop ; 3
and #$1f ;============
clc ; 7
adc hgr_offsets_h,Y
sta GBASH
ldy #0 ; -1
lda #0
sta (GBASL),Y
inx
cpx #NUMFLAKES
bne erase_loop
;========================== ;==========================
; move snow ; move snow
@@ -97,11 +132,11 @@ just_inc:
jmp snow_no jmp snow_no
snow_right: snow_right:
inc snow_offset,X inc snow_x,X
jmp snow_no jmp snow_no
snow_left: snow_left:
dec snow_offset,X dec snow_x,X
snow_no: snow_no:
done_inc: done_inc:
@@ -112,35 +147,54 @@ done_inc:
;========================= ;=========================
; draw new snow ; draw new snow
;=========================
; 2+ (35+22+19+7)*NUMFLAKES -1
; 1+83*NUMFLAKES = 831
ldx #0 ldx #0 ; 2
draw_loop: draw_loop:
lda snow_y,X lda snow_y,X ; 4+
lsr lsr ; 2
lsr lsr ; 2
lsr lsr ; 2
tay sta TEMPY ; 3
clc lda snow_x,X ; 4+
lda hgr_offsets_l,Y tay ; 2
adc snow_x,X lda div_7_q,Y ; 4+
sta GBASL ldy TEMPY ; 3
clc ; 2
adc hgr_offsets_l,Y ; 4+
sta GBASL ; 3
;===========
; 35
lda snow_y,X lda snow_y,X ; 4+
asl asl ; 2
asl asl ; 2
and #$1f and #$1f ; 2
clc clc ; 2
adc hgr_offsets_h,Y adc hgr_offsets_h,Y ; 4+
sta GBASH sta GBASH ; 3
;=============
; 19
ldy #0 ldy snow_x,X ; 4+
lda #1 lda div_7_r,Y ; 4+
sta (GBASL),Y tay ; 2
lda pixel_lookup,Y ; 4+
inx ldy #0 ; 2
cpx #NUMFLAKES sta (GBASL),Y ; 6
bne draw_loop ;=============
; 22
inx ; 2
cpx #NUMFLAKES ; 2
bne draw_loop ; 3
;=============
; 7
; -1
lda #100 lda #100
jsr WAIT jsr WAIT
@@ -148,10 +202,7 @@ draw_loop:
snow_x: snow_x:
.byte 2,4,6,8,10,12,14,16,18,20 .byte 0,0,0,0,0,0,0,0,0,0
snow_offset:
.byte 0,1,2,3,4,5,6,7,0,1
snow_y: snow_y:
.byte 0,0,0,0,0,0,0,0,0,0 .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 0,1,2,3,4,5,6 ; 56..62
.byte 0 ; 63 .byte 0 ; 63
pixel_lookup:
.byte $01,$02,$04,$08,$10,$20,$40
.include "random16.s" .include "random16.s"