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xmas2019: work on snow

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This commit is contained in:
Vince Weaver 2019-12-20 13:01:11 -05:00
parent b87f6bd166
commit 90343afb67
1 changed files with 95 additions and 31 deletions
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126
xmas_2019/snow.s
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@ -62,8 +62,8 @@ display_loop:
;=========================
; erase old snow
;=========================
; 2 + (35+29+7)*NUMFLAKES - 1
; 1 +71*NUMFLAKES = 711
; 2 + (40+38+7)*NUMFLAKES - 1
; 1 + 85*NUMFLAKES = 851
ldx #0 ; 2
erase_loop:
@ -75,12 +75,15 @@ erase_loop:
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
adc #30 ; 2
sta BASL ; 3
;=============
; 35
; 40
lda snow_y,X ; 4+
asl ; 2
@ -89,11 +92,14 @@ erase_loop:
clc ; 2
adc hgr_offsets_h,Y ; 4
sta GBASH ; 3
sta BASH ; 3
lda #0 ; 2
tay ; 2
sta (GBASL),Y ; 6
sta (BASL),Y ; 6
;============
; 29
; 38
inx ; 2
cpx #NUMFLAKES ; 2
@ -105,51 +111,105 @@ erase_loop:
;==========================
; move snow
;
; 2 + NUM_FLAKES*(9+17+56+15+11+7) -1
; 1 + NUM_FLAKES*115 = 1151
ldx #0
ldx #0 ; 2
move_snow:
lda snow_y,X ; inc to next line
cmp #191
bne just_inc
lda #0
sta snow_y,X
jmp done_inc
; Check if off edge of screen
lda snow_y,X ; 4+
cmp #160 ; 2
beq snow_new_y ; 3
;==========
; 9
no_new_y:
; -1
lda SEEDH ; 3
lda SEEDH ; 3
lda SEEDH ; 3
lda SEEDH ; 3
lda SEEDH ; 3
jmp just_inc ; 3
;============
; 17
snow_new_y:
; out of bounds, get new
lda #32 ; 2
sta snow_y,X ; 5
lda SEEDH ; 3
and #$3f ; 2
sta snow_x,X ; 5
;============
; 17
just_inc:
jsr random16
lda SEEDL
and #$f
jsr random16 ; 6+42
lda SEEDL ; 3
and #$f ; 2
beq snow_left ; 3
;===============
; 56
beq snow_left
cmp #$1
beq snow_right
; if left = 6 = 6 + (9) = 15
; if right = 4+9 = 13 + (2) = 15
; else = 4+8 = 12 + (3) = 15
; -1
cmp #$1 ; 2
beq snow_right ; 3
;===============
; 4
inc snow_y,X
jmp snow_no
snow_else:
lda SEEDL ; nop ; 3
; -1
inc snow_y,X ; 6
jmp snow_no ; 3
;===============
; 8+3
snow_right:
inc snow_x,X
jmp snow_no
nop ; 2
inc snow_x,X ; 6
jmp snow_no ; 3
;============
; 9+2
snow_left:
dec snow_x,X
dec snow_x,X ; 6
lda SEEDL ; nop
lda SEEDL ; nop
lda SEEDL ; nop
snow_no:
lda snow_x,X ; 4+
and #$3f ; 2
sta snow_x,X ; 5
;====
; 11
done_inc:
inx
cpx #NUMFLAKES
bne move_snow
inx ; 2
cpx #NUMFLAKES ; 2
bne move_snow ; 3
;===========
; 7
; -1
;=========================
; draw new snow
;=========================
; 2+ (35+22+19+7)*NUMFLAKES -1
; 1+83*NUMFLAKES = 831
; 2+ (40+22+28+7)*NUMFLAKES -1
; 1+97*NUMFLAKES = 971
ldx #0 ; 2
draw_loop:
@ -165,8 +225,10 @@ draw_loop:
clc ; 2
adc hgr_offsets_l,Y ; 4+
sta GBASL ; 3
adc #30 ; 2
sta BASL ; 3
;===========
; 35
; 40
lda snow_y,X ; 4+
asl ; 2
@ -175,8 +237,9 @@ draw_loop:
clc ; 2
adc hgr_offsets_h,Y ; 4+
sta GBASH ; 3
sta BASH ; 3
;=============
; 19
; 22
ldy snow_x,X ; 4+
lda div_7_r,Y ; 4+
@ -185,8 +248,9 @@ draw_loop:
ldy #0 ; 2
sta (GBASL),Y ; 6
sta (BASL),Y ; 6
;=============
; 22
; 28
inx ; 2
cpx #NUMFLAKES ; 2