Spaces

1 files changed, 913 insertions, 913 deletions

diff --git a/video.asm b/video.asm
index 9c4fd40..2c0be23 100644
--- a/video.asm
+++ b/video.asm
@@ -1,913 +1,913 @@
-	; cursors target coordinates

-SPRITE_0_X_TARGET .rs 1

-SPRITE_0_Y_TARGET .rs 1

-SPRITE_1_X_TARGET .rs 1

-SPRITE_1_Y_TARGET .rs 1

-	; variables for game name drawing

-TEXT_DRAW_GAME .rs 2

-TEXT_DRAW_ROW .rs 1

-SCROLL_LINES .rs 2 ; current scroll line

-SCROLL_LINES_MODULO .rs 1 ; current scroll line % 30

-LAST_LINE_MODULO .rs 1

-LAST_LINE_GAME .rs 2

-SCROLL_FINE .rs 1 ; fine scroll position

-SCROLL_LINES_TARGET .rs 2 ; scrolling target

-STAR_SPAWN_TIMER .rs 1 ; stars spawn timer

-

-	; constants

-CHARS_PER_LINE .equ 32

-LINES_PER_SCREEN .equ 30

-LINES_PER_VISIBLE_SCREEN .equ 15

-

-waitblank: 

-	pha

-	tya

-	pha

-	txa

-	pha

-

-	bit $2002 ; reset vblank bit

-.loop:

-	lda $2002 ; load A with value at location $2002

-	bpl .loop  ; if bit 7 is not set (not VBlank) keep checking

-	

-	; scrolling

-	jsr move_scrolling

-	jsr scroll_fix	

-	; updating sprites

-	jsr sprite_dma_copy

-	; moving cursors

-	jsr move_cursors

-	; reading controller 

-	jsr read_controller

-	; stars on the background

-	.if	ENABLE_STARS!=0

-	jsr stars

-	.endif

-	

-	pla

-	tax

-	pla

-	tay

-	pla

-	;plp

-	rts

-	

-waitblank_simple:

-	pha

-	bit $2002

-.loop:

-	lda $2002  ; load A with value at location $2002

-	bpl .loop  ; if bit 7 is not set (not VBlank) keep checking

-	pla

-	rts

-

-scroll_fix:

-	; scrollong reset

-	bit $2002	

-	lda #0

-	sta $2005

-	lda <SCROLL_LINES_MODULO

-	cmp #LINES_PER_VISIBLE_SCREEN

-	bcc .first_screen ; <?

-	sec

-	sbc #LINES_PER_VISIBLE_SCREEN ; substracting otherwise

-	ldy #%00001010 ; second nametable

-	jmp .really	

-.first_screen:

-	ldy #%00001000 ; first nametable	

-.really:

-	sty $2000

-	asl A

-	asl A

-	asl A

-	asl A

-	clc

-	adc <SCROLL_FINE

-	.if ENABLE_TOP_OFFSET!=0

-	sec    ; для больших картинок сверху

-	sbc #8 ; для больших картинок сверху

-	.endif

-	sta $2005

-	rts

-

-scroll_line_down:

-	lda <SCROLL_LINES

-	clc

-	adc #1

-	sta <SCROLL_LINES

-	lda <SCROLL_LINES+1

-	adc #0

-	sta <SCROLL_LINES+1

-	inc <SCROLL_LINES_MODULO

-	lda <SCROLL_LINES_MODULO

-	cmp #LINES_PER_SCREEN

-	bcc .modulo_ok

-	lda #0

-	sta <SCROLL_LINES_MODULO

-.modulo_ok:

-	lda <LAST_LINE_GAME

-	clc

-	adc #1

-	sta <LAST_LINE_GAME

-	lda <LAST_LINE_GAME+1

-	adc #0

-	sta <LAST_LINE_GAME+1

-	inc <LAST_LINE_MODULO

-	lda <LAST_LINE_MODULO

-	cmp #LINES_PER_SCREEN

-	bcc .modulo_ok2

-	lda #0

-	sta <LAST_LINE_MODULO

-.modulo_ok2:	

-	jsr print_last_name

-	rts

-

-scroll_line_up:

-	lda <SCROLL_LINES

-	sec

-	sbc #1

-	sta <SCROLL_LINES

-	lda <SCROLL_LINES+1

-	sbc #0

-	sta <SCROLL_LINES+1

-	dec <SCROLL_LINES_MODULO

-	lda <SCROLL_LINES_MODULO

-	bpl .modulo_ok

-	lda #LINES_PER_SCREEN

-	sta <SCROLL_LINES_MODULO

-	dec <SCROLL_LINES_MODULO

-.modulo_ok:

-	lda <LAST_LINE_GAME

-	sec

-	sbc #1

-	sta <LAST_LINE_GAME

-	lda <LAST_LINE_GAME+1

-	sbc #0

-	sta <LAST_LINE_GAME+1

-	dec <LAST_LINE_MODULO

-	lda <LAST_LINE_MODULO

-	bpl .modulo_ok2

-	lda #LINES_PER_SCREEN

-	sta <LAST_LINE_MODULO

-	dec <LAST_LINE_MODULO

-.modulo_ok2:	

-	jsr print_first_name

-	rts

-

-load_base_chr:

-	; loading CHR

-	lda #$06

-	jsr select_bank

-	lda #LOW(chr_data)

-	sta COPY_SOURCE_ADDR

-	lda #HIGH(chr_data)

-	sta COPY_SOURCE_ADDR+1

-	jsr load_chr

-	rts

-

-load_base_pal:

-	; loading palette into $3F00 of PPU

-	lda #$3F

-	sta $2006

-	lda #$00

-	sta $2006

-	ldx #$00

-loadpal:

-	lda tilepal, x

-	sta $2007

-	inx

-	cpx #32

-	bne loadpal

-

-	; letters colors

-	lda #$3F

-	sta $2006

-	lda #$0D

-	sta $2006

-	ldx #17

-loadpal2:

-	lda tilepal, x

-	sta $2007

-	inx

-	cpx #20

-	bne loadpal2

-	rts

-

-load_black:

-	; loading empty black palette into $3F00 of PPU

-	lda #$3F

-	sta $2006

-	lda #$00

-	sta $2006

-	ldx #$00

-	lda #$3F ; color

-load_black_pal:

-	sta $2007

-	inx

-	cpx #32

-	bne load_black_pal

-	rts

-

-	; nametable cleanup

-clear_screen:

-	lda #$20

-	sta $2006

-	lda #$00

-	sta $2006

-	lda #$00

-	ldx #0

-	ldy #$10

-.loop:

-	sta $2007

-	inx

-	bne .loop

-	dey

-	bne .loop

-	rts

-	

-	; clear all sprites data

-clear_sprites:

-	lda #$FF

-	ldx #0

-.loop:

-	sta SPRITES, x

-	inx

-	bne .loop

-	rts

-

-	; DMA sprites loading

-sprite_dma_copy:

-	ldx #0

-	stx $2003	

-	ldx #HIGH(SPRITES)

-	stx $4014

-	rts

-	

-	; loading header (image on the top), first part

-draw_header1:

-	lda #$06

-	jsr select_bank

-	bit $2002

-	lda #$20

-	sta $2006

-	lda #$00

-	sta $2006

-	ldx #0

-	ldy #$40

-.loop:

-	lda nametable, x

-	sta $2007

-	inx

-	dey

-	bne .loop

-	rts

-	

-	; loading header (image on the top), second part

-draw_header2:

-	lda #$06

-	jsr select_bank

-	bit $2002

-	lda #$20

-	sta $2006

-	lda #$40

-	sta $2006

-	ldx #$40

-	ldy #$40

-.loop:

-	lda nametable, x

-	sta $2007

-	inx

-	dey

-	bne .loop

-	; loading attributes for it

-	lda #$23

-	sta $2006

-	lda #$C0

-	sta $2006

-	ldx #0

-	ldy #8

-.palette_loop:

-	lda nametable+$3C0, x

-	sta $2007

-	inx

-	dey

-	bne .palette_loop

-	rts

-

-	; loading footer (image on the bottom), first part

-draw_footer1:

-	lda #$06

-	jsr select_bank

-	ldx #0

-	ldy #$40

-.loop:

-	lda nametable+$340, x

-	sta $2007

-	inx

-	dey

-	bne .loop

-	rts

-

-	; loading footer (image on the bottom), second part

-draw_footer2:

-	lda #$06

-	jsr select_bank

-	ldx #0

-	ldy #$40

-.loop:

-	lda nametable+$380, x

-	sta $2007

-	inx

-	dey

-	bne .loop

-	rts

-

-	; printing game name on the top

-print_first_name:

-	pha

-	lda <SCROLL_LINES

-	sta <TEXT_DRAW_GAME

-	lda <SCROLL_LINES+1

-	sta <TEXT_DRAW_GAME+1

-	lda <SCROLL_LINES_MODULO

-	sta <TEXT_DRAW_ROW

-	jsr print_name

-	pla

-	rts

-

-	; printing game name on the bottom

-print_last_name:

-	pha

-	lda <LAST_LINE_GAME

-	sta <TEXT_DRAW_GAME

-	lda <LAST_LINE_GAME+1

-	sta <TEXT_DRAW_GAME+1

-	lda <LAST_LINE_MODULO

-	sta <TEXT_DRAW_ROW

-	jsr print_name

-	pla

-	rts

-

-print_name:

-	pha

-	tya

-	pha

-	txa

-	pha	

-	; is it header lines?

-	lda <TEXT_DRAW_GAME+1

-	bne .not_header ; no

-	lda <TEXT_DRAW_GAME

-	beq .header1

-	cmp #1

-	beq .header2

-	jmp .not_header	

-.header1:

-	jsr draw_header1

-	jmp .end_really_really

-.header2:

-	jsr draw_header2

-	jmp .end_really_really

-.not_header:

-	; when there are not so many games we need so offset

-	lda <TEXT_DRAW_ROW

-	clc

-	adc games_offset

-	sta <TEXT_DRAW_ROW

-	asl <TEXT_DRAW_ROW ; x2

-	lda <TEXT_DRAW_ROW

-	; detecting target nametable

-	cmp #LINES_PER_SCREEN

-	bcc .first_screen

-	; second

-	sec

-	sbc #LINES_PER_SCREEN

-	lsr A

-	lsr A

-	lsr A

-	clc

-	adc #$2C

-	bit $2002

-	sta $2006

-	lda <TEXT_DRAW_ROW

-	sec

-	sbc #LINES_PER_SCREEN

-	asl A

-	asl A

-	asl A

-	asl A

-	asl A

-	sta $2006

-	jmp .print_end

-	; first

-.first_screen:

-	lsr A

-	lsr A

-	lsr A

-	clc

-	adc #$20

-	bit $2002

-	sta $2006

-	lda <TEXT_DRAW_ROW

-	asl A

-	asl A

-	asl A

-	asl A

-	asl A

-	sta $2006

-.print_end:

-	; we need to substract 2 from game number

-	lda <TEXT_DRAW_GAME

-	sec

-	sbc #2

-	sta <TEXT_DRAW_GAME

-	lda <TEXT_DRAW_GAME+1

-	sbc #0

-	sta <TEXT_DRAW_GAME+1

-	; is it footer?

-	lda <TEXT_DRAW_GAME

-	sec

-	sbc games_count

-	lda <TEXT_DRAW_GAME+1

-	sbc games_count+1

-	bcc .print_text_line

-	ldx <TEXT_DRAW_GAME

-	cpx games_count

-	beq .footer1

-	dex

-	cpx games_count

-	beq .footer2

-	jmp .end

-.footer2:

-	jsr draw_footer2

-	; lets keep for footer text palette, i like how it looks

-	jmp .end

-.footer1:

-	jsr draw_footer1

-	jmp .end

-.print_text_line:

-	lda <TEXT_DRAW_GAME+1

-	jsr select_bank

-	lda #LOW(game_names)

-	clc

-	adc <TEXT_DRAW_GAME

-	sta <TMP

-	lda #HIGH(game_names)

-	adc #0

-	sta <TMP+1

-	lda <TMP

-	clc 

-	adc <TEXT_DRAW_GAME

-	sta <TMP

-	lda <TMP+1

-	adc #0

-	sta <TMP+1	

-	ldy #0

-	lda [TMP], y

-	sta COPY_SOURCE_ADDR

-	iny

-	lda [TMP], y

-	sta COPY_SOURCE_ADDR+1

-	; spaces on the left

-	ldx #GAME_NAMES_OFFSET+1

-.print_blank:

-	lda #$00

-	sta $2007

-	dex

-	bne .print_blank	

-	; text

-	ldx #GAME_NAMES_OFFSET+1

-	ldy #0

-	lda #1

-.next_char:

-	cmp #0 ; after zero we are not printing letters but printing spaces

-	beq .end_of_line

-	lda [COPY_SOURCE_ADDR], y

-.end_of_line:

-	sta $2007	

-	iny

-	inx

-	cpx #CHARS_PER_LINE

-	bne .next_char

-.end:

-	; but if it upper part, we need to erase two lines

-	lda <TEXT_DRAW_ROW

-	cmp #4

-	bcs .end_really

-	ldy #CHARS_PER_LINE

-	lda #0

-.clear_2nd_line:

-	sta $2007

-	dey

-	bne .clear_2nd_line

-.end_really:

-	; attributes for text

-	lda <TEXT_DRAW_ROW

-	cmp #LINES_PER_SCREEN

-	bcc .print_palette_addr_first_screen

-	; second nametable

-	lda #$2F

-	sta $2006

-	lda <TEXT_DRAW_ROW

-	sec

-	sbc #LINES_PER_SCREEN

-	jmp .print_palette_addr_select_end

-	; first nametable

-.print_palette_addr_first_screen:

-	lda #$23

-	sta $2006

-	lda <TEXT_DRAW_ROW

-.print_palette_addr_select_end:

-	; one byte for 4 rows

-	lsr A

-	lsr A

-	asl A

-	asl A

-	asl A

-	clc

-	adc #$C0

-	sta $2006

-	lda #$FF

-	sta $2007

-	sta $2007

-	sta $2007

-	sta $2007

-	sta $2007

-	sta $2007

-	sta $2007

-	sta $2007	

-.end_really_really:

-	pla

-	tax

-	pla

-	tay

-	pla

-	rts

-

-move_cursors:

-	; fine cursor scrolling

-	lda <SPRITE_1_X_TARGET

-	cmp SPRITE_1_X

-	beq .sprite_1x_target_end

-	bcs .sprite_1x_target_plus

-	lda SPRITE_1_X

-	sec

-	sbc #4

-	sta SPRITE_1_X

-	jmp .sprite_1x_target_end

-.sprite_1x_target_plus:

-	lda SPRITE_1_X

-	clc

-	adc #4

-	sta SPRITE_1_X

-.sprite_1x_target_end:

-	lda <SPRITE_1_Y_TARGET

-	cmp SPRITE_1_Y

-	beq .sprite_1y_target_end

-	bcs .sprite_1y_target_plus

-	lda SPRITE_1_Y

-	sec

-	sbc #4

-	sta SPRITE_0_Y

-	sta SPRITE_1_Y

-	jmp .sprite_1y_target_end

-.sprite_1y_target_plus:

-	lda SPRITE_1_Y

-	clc

-	adc #4

-	sta SPRITE_0_Y

-	sta SPRITE_1_Y

-.sprite_1y_target_end:

-	rts

-

-	; fine scrolling to target line

-move_scrolling:

-	; determining scroll speed

-	lda <SCROLL_LINES

-	clc

-	adc #2

-	sta <TMP

-	lda <SCROLL_LINES+1

-	adc #0

-	sta <TMP+1

-	lda <SCROLL_LINES_TARGET

-	sec

-	sbc <TMP

-	lda <SCROLL_LINES_TARGET+1

-	sbc <TMP+1

-	bcs .move_scrolling_fast_down

-	lda <SCROLL_LINES_TARGET

-	clc

-	adc #2

-	sta <TMP

-	lda <SCROLL_LINES_TARGET+1

-	adc #0

-	sta <TMP+1

-	lda <SCROLL_LINES

-	sec

-	sbc <TMP

-	lda <SCROLL_LINES+1

-	sbc <TMP+1

-	bcs .move_scrolling_fast_up	

-	; slow scrolling

-	jsr .move_scrolling_real

-	rts	

-	; fast scrolling

-.move_scrolling_fast:

-	jsr .move_scrolling_real

-	jsr .move_scrolling_real

-	jsr .move_scrolling_real

-	jsr .move_scrolling_real

-	rts

-.move_scrolling_fast_up:

-	jmp scroll_line_up

-.move_scrolling_fast_down:

-	jmp scroll_line_down

-.move_scrolling_real:

-	; do we need to move screen?

-	ldx <SCROLL_LINES_TARGET

-	cpx <SCROLL_LINES

-	bne .need

-	ldx <SCROLL_LINES_TARGET+1

-	cpx <SCROLL_LINES+1

-	bne .need

-	ldx <SCROLL_FINE

-	bne .need

-	rts	

-	; we need it

-.need:

-	lda <SCROLL_LINES

-	sec

-	sbc <SCROLL_LINES_TARGET

-	lda <SCROLL_LINES+1

-	sbc <SCROLL_LINES_TARGET+1

-	bcc .target_plus

-	; scrolling up

-	lda <SCROLL_FINE

-	sec

-	sbc #4

-	bmi .target_minus

-	sta <SCROLL_FINE

-	rts	

-.target_minus:

-	and #$0f

-	sta <SCROLL_FINE

-	jsr scroll_line_up

-	rts		

-.target_plus:

-	; scrolling down

-	lda <SCROLL_FINE

-	; adding fine value

-	clc

-	adc #4

-	sta <SCROLL_FINE

-	cmp #16

-	bne .end

-	; down if fine >=16

-	lda #0

-	sta <SCROLL_FINE	

-	jsr scroll_line_down

-.end:

-	rts

-

-set_cursor_targets:

-	; set scroll targets first

-.not_ok1:

-	lda <SCROLL_LINES_TARGET

-	clc

-	adc #10

-	sta <TMP

-	lda <SCROLL_LINES_TARGET+1

-	adc #0

-	sta <TMP+1

-	lda <TMP

-	sec

-	sbc <SELECTED_GAME

-	lda <TMP+1

-	sbc <SELECTED_GAME+1

-	bcs .ok1 ; надо скроллить вниз

-	lda <SCROLL_LINES_TARGET

-	clc

-	adc #1

-	sta <SCROLL_LINES_TARGET

-	lda <SCROLL_LINES_TARGET+1

-	adc #0

-	sta <SCROLL_LINES_TARGET+1

-	jmp .not_ok1	

-.ok1:

-.not_ok2:

-	lda <SELECTED_GAME

-	sec

-	sbc <SCROLL_LINES_TARGET

-	lda <SELECTED_GAME+1

-	sbc <SCROLL_LINES_TARGET+1

-	bcs .ok2 ; надо скроллить вверх

-	lda <SCROLL_LINES_TARGET

-	sec

-	sbc #1

-	sta <SCROLL_LINES_TARGET

-	lda <SCROLL_LINES_TARGET+1

-	sbc #0

-	sta <SCROLL_LINES_TARGET+1

-	jmp .not_ok2

-.ok2:

-	; set cursor targets depending on selected game number

-	; left cursor, X

-	ldx <SELECTED_GAME

-	lda #GAME_NAMES_OFFSET*8

-	sta <SPRITE_0_X_TARGET	

-	; right cursor, X

-	lda <SELECTED_GAME+1

-	jsr select_bank

-	ldx <SELECTED_GAME

-	ldy loader_data_cursor_pos, x

-	dey

-	tya

-	clc

-	adc #GAME_NAMES_OFFSET+2

-	asl A

-	asl A

-	asl A

-	sta <SPRITE_1_X_TARGET	

-	; Y coordinate it the same for both

-	lda <SELECTED_GAME	

-	; when there are not so many games

-	clc

-	adc games_offset	

-	sec 

-	sbc <SCROLL_LINES_TARGET

-	clc

-	adc #2

-	asl A

-	asl A

-	asl A

-	asl A

-	sec

-	sbc #1

-	.if ENABLE_TOP_OFFSET!=0 ; for large images on top

-	clc

-	adc #8

-	.endif

-	sta <SPRITE_0_Y_TARGET

-	sta <SPRITE_1_Y_TARGET

-	rts

-	

-stars:

-	lda <STAR_SPAWN_TIMER

-	cmp #$E0 ; stars count

-	beq .spawn_end	

-	inc <STAR_SPAWN_TIMER

-	lda <STAR_SPAWN_TIMER

-	and #$0F

-	cmp #0

-	bne .spawn_end

-	lda <STAR_SPAWN_TIMER

-	lsr A

-	lsr A

-	tay

-	lda <STAR_SPAWN_TIMER

-	lda #$FC ; Y, below screen

-	sta SPRITES+4, y

-	iny

-	jsr random ; random tile

-	and #$03

-	clc

-	adc #$71

-	sta SPRITES+4, y

-	iny

-	jsr random  ; attributes, random palette

-	and #%00000011 ; palette - tho lowest bits

-	ora #%00100000 ; low priority bit

-	sta SPRITES+4, y

-	iny

-	jsr random

-	sta SPRITES+4, y

-.spawn_end:

-	ldy #8

-.move_next:

-	lda SPRITES, y

-	cmp #$FF

-	beq .move_end

-	tya

-	lsr A

-	lsr A

-	and #$07

-	cmp #$00

-	beq .move_fast

-	cmp #$01

-	beq .move_fast

-	cmp #$02

-	beq .move_fast

-	cmp #$03

-	beq .move_medium

-	cmp #$04

-	beq .move_medium

-	cmp #$05

-	beq .move_slow

-	cmp #$06

-	beq .move_slow	

-.move_very_slow: ; default

-	lda SPRITES, y

-	sbc #1

-	jmp .moved

-.move_slow:

-	lda SPRITES, y

-	sec

-	sbc #2

-	jmp .moved

-.move_medium:

-	lda SPRITES, y

-	sec

-	sbc #3

-	jmp .moved

-.move_fast:

-	lda SPRITES, y

-	sec

-	sbc #4

-.moved:

-	sta SPRITES, y

-	cmp #$0A

-	bcs .move_next1

-	lda #$FC

-	sta SPRITES, y ; reset Y

-	jsr random  ; random tile

-	and #$03

-	clc

-	adc #$71

-	sta SPRITES+1, y

-	jsr random ; random X

-	sta SPRITES+3, y

-	jsr random ; random attributes

-	and #%00000011 ; palette - lowest tho bits

-	ora #%00100000 ; priority bit

-	sta SPRITES+2, y

-.move_next1:

-	iny

-	iny

-	iny

-	iny

-	bne .move_next	

-.move_end:

-	rts

-

-load_text_palette:

-	lda #$23

-	sta $2006

-	lda #$C8

-	sta $2006

-	lda #$FF

-	ldy #$38

-.print_warning_palette:

-	sta $2007

-	dey

-	bne .print_warning_palette

-  rts

-

-  ; print null-terminated string from [COPY_SOURCE_ADDR]

-print_text:

-	ldy #0

-.loop:

-  lda [COPY_SOURCE_ADDR], y

-  sta $2007

-  iny

-  cmp #0 ; stop at zero

-  bne .loop

-  rts

-

-saving_warning_show:

-  ; disable PPU

-	lda #%00000000

-	sta $2000

-	sta $2001

-	jsr waitblank_simple

-	jsr clear_screen

-	lda #$21

-	sta $2006

-	lda #$C0

-	sta $2006

-  lda #LOW(saving_text)

-  sta COPY_SOURCE_ADDR

-  lda #HIGH(saving_text)

-  sta COPY_SOURCE_ADDR+1

-  jsr print_text

-  jsr load_text_palette

-	jsr waitblank_simple

-	bit $2002

-	lda #0

-	sta $2005

-	sta $2005

-	lda #%00001000

-	sta $2000

-	lda #%00001010

-	sta $2001

-	jsr waitblank_simple

-	rts

-

-saving_warning_hide:

-	lda #%00000000 ; disable PPU

-	sta $2000

-	sta $2001

-	jsr waitblank_simple

-	jsr clear_screen

-	rts

+  ; cursors target coordinates
+SPRITE_0_X_TARGET .rs 1
+SPRITE_0_Y_TARGET .rs 1
+SPRITE_1_X_TARGET .rs 1
+SPRITE_1_Y_TARGET .rs 1
+  ; variables for game name drawing
+TEXT_DRAW_GAME .rs 2
+TEXT_DRAW_ROW .rs 1
+SCROLL_LINES .rs 2 ; current scroll line
+SCROLL_LINES_MODULO .rs 1 ; current scroll line % 30
+LAST_LINE_MODULO .rs 1
+LAST_LINE_GAME .rs 2
+SCROLL_FINE .rs 1 ; fine scroll position
+SCROLL_LINES_TARGET .rs 2 ; scrolling target
+STAR_SPAWN_TIMER .rs 1 ; stars spawn timer
+
+  ; constants
+CHARS_PER_LINE .equ 32
+LINES_PER_SCREEN .equ 30
+LINES_PER_VISIBLE_SCREEN .equ 15
+
+waitblank: 
+  pha
+  tya
+  pha
+  txa
+  pha
+
+  bit $2002 ; reset vblank bit
+.loop:
+  lda $2002 ; load A with value at location $2002
+  bpl .loop  ; if bit 7 is not set (not VBlank) keep checking
+  
+  ; scrolling
+  jsr move_scrolling
+  jsr scroll_fix  
+  ; updating sprites
+  jsr sprite_dma_copy
+  ; moving cursors
+  jsr move_cursors
+  ; reading controller 
+  jsr read_controller
+  ; stars on the background
+  .if  ENABLE_STARS!=0
+  jsr stars
+  .endif
+  
+  pla
+  tax
+  pla
+  tay
+  pla
+  ;plp
+  rts
+  
+waitblank_simple:
+  pha
+  bit $2002
+.loop:
+  lda $2002  ; load A with value at location $2002
+  bpl .loop  ; if bit 7 is not set (not VBlank) keep checking
+  pla
+  rts
+
+scroll_fix:
+  ; scrollong reset
+  bit $2002  
+  lda #0
+  sta $2005
+  lda <SCROLL_LINES_MODULO
+  cmp #LINES_PER_VISIBLE_SCREEN
+  bcc .first_screen ; <?
+  sec
+  sbc #LINES_PER_VISIBLE_SCREEN ; substracting otherwise
+  ldy #%00001010 ; second nametable
+  jmp .really  
+.first_screen:
+  ldy #%00001000 ; first nametable  
+.really:
+  sty $2000
+  asl A
+  asl A
+  asl A
+  asl A
+  clc
+  adc <SCROLL_FINE
+  .if ENABLE_TOP_OFFSET!=0
+  ; for large images on the top
+  sec
+  sbc #8 
+  .endif
+  sta $2005
+  rts
+
+scroll_line_down:
+  lda <SCROLL_LINES
+  clc
+  adc #1
+  sta <SCROLL_LINES
+  lda <SCROLL_LINES+1
+  adc #0
+  sta <SCROLL_LINES+1
+  inc <SCROLL_LINES_MODULO
+  lda <SCROLL_LINES_MODULO
+  cmp #LINES_PER_SCREEN
+  bcc .modulo_ok
+  lda #0
+  sta <SCROLL_LINES_MODULO
+.modulo_ok:
+  lda <LAST_LINE_GAME
+  clc
+  adc #1
+  sta <LAST_LINE_GAME
+  lda <LAST_LINE_GAME+1
+  adc #0
+  sta <LAST_LINE_GAME+1
+  inc <LAST_LINE_MODULO
+  lda <LAST_LINE_MODULO
+  cmp #LINES_PER_SCREEN
+  bcc .modulo_ok2
+  lda #0
+  sta <LAST_LINE_MODULO
+.modulo_ok2:  
+  jsr print_last_name
+  rts
+
+scroll_line_up:
+  lda <SCROLL_LINES
+  sec
+  sbc #1
+  sta <SCROLL_LINES
+  lda <SCROLL_LINES+1
+  sbc #0
+  sta <SCROLL_LINES+1
+  dec <SCROLL_LINES_MODULO
+  lda <SCROLL_LINES_MODULO
+  bpl .modulo_ok
+  lda #LINES_PER_SCREEN
+  sta <SCROLL_LINES_MODULO
+  dec <SCROLL_LINES_MODULO
+.modulo_ok:
+  lda <LAST_LINE_GAME
+  sec
+  sbc #1
+  sta <LAST_LINE_GAME
+  lda <LAST_LINE_GAME+1
+  sbc #0
+  sta <LAST_LINE_GAME+1
+  dec <LAST_LINE_MODULO
+  lda <LAST_LINE_MODULO
+  bpl .modulo_ok2
+  lda #LINES_PER_SCREEN
+  sta <LAST_LINE_MODULO
+  dec <LAST_LINE_MODULO
+.modulo_ok2:  
+  jsr print_first_name
+  rts
+
+load_base_chr:
+  ; loading CHR
+  lda #$06
+  jsr select_bank
+  lda #LOW(chr_data)
+  sta COPY_SOURCE_ADDR
+  lda #HIGH(chr_data)
+  sta COPY_SOURCE_ADDR+1
+  jsr load_chr
+  rts
+
+load_base_pal:
+  ; loading palette into $3F00 of PPU
+  lda #$3F
+  sta $2006
+  lda #$00
+  sta $2006
+  ldx #$00
+.loop:
+  lda tilepal, x
+  sta $2007
+  inx
+  cpx #32
+  bne .loop
+  ; letters colors
+  lda #$3F
+  sta $2006
+  lda #$0D
+  sta $2006
+  ldx #17
+.loop2:
+  lda tilepal, x
+  sta $2007
+  inx
+  cpx #20
+  bne .loop2
+  rts
+
+load_black:
+  ; loading empty black palette into $3F00 of PPU
+  lda #$3F
+  sta $2006
+  lda #$00
+  sta $2006
+  ldx #$00
+  lda #$3F ; color
+.loop:
+  sta $2007
+  inx
+  cpx #32
+  bne .loop
+  rts
+
+  ; nametable cleanup
+clear_screen:
+  lda #$20
+  sta $2006
+  lda #$00
+  sta $2006
+  lda #$00
+  ldx #0
+  ldy #$10
+.loop:
+  sta $2007
+  inx
+  bne .loop
+  dey
+  bne .loop
+  rts
+  
+  ; clear all sprites data
+clear_sprites:
+  lda #$FF
+  ldx #0
+.loop:
+  sta SPRITES, x
+  inx
+  bne .loop
+  rts
+
+  ; DMA sprites loading
+sprite_dma_copy:
+  ldx #0
+  stx $2003  
+  ldx #HIGH(SPRITES)
+  stx $4014
+  rts
+  
+  ; loading header (image on the top), first part
+draw_header1:
+  lda #$06
+  jsr select_bank
+  bit $2002
+  lda #$20
+  sta $2006
+  lda #$00
+  sta $2006
+  ldx #0
+  ldy #$40
+.loop:
+  lda nametable, x
+  sta $2007
+  inx
+  dey
+  bne .loop
+  rts
+  
+  ; loading header (image on the top), second part
+draw_header2:
+  lda #$06
+  jsr select_bank
+  bit $2002
+  lda #$20
+  sta $2006
+  lda #$40
+  sta $2006
+  ldx #$40
+  ldy #$40
+.loop:
+  lda nametable, x
+  sta $2007
+  inx
+  dey
+  bne .loop
+  ; loading attributes for it
+  lda #$23
+  sta $2006
+  lda #$C0
+  sta $2006
+  ldx #0
+  ldy #8
+.palette_loop:
+  lda nametable+$3C0, x
+  sta $2007
+  inx
+  dey
+  bne .palette_loop
+  rts
+
+  ; loading footer (image on the bottom), first part
+draw_footer1:
+  lda #$06
+  jsr select_bank
+  ldx #0
+  ldy #$40
+.loop:
+  lda nametable+$340, x
+  sta $2007
+  inx
+  dey
+  bne .loop
+  rts
+
+  ; loading footer (image on the bottom), second part
+draw_footer2:
+  lda #$06
+  jsr select_bank
+  ldx #0
+  ldy #$40
+.loop:
+  lda nametable+$380, x
+  sta $2007
+  inx
+  dey
+  bne .loop
+  rts
+
+  ; printing game name on the top
+print_first_name:
+  pha
+  lda <SCROLL_LINES
+  sta <TEXT_DRAW_GAME
+  lda <SCROLL_LINES+1
+  sta <TEXT_DRAW_GAME+1
+  lda <SCROLL_LINES_MODULO
+  sta <TEXT_DRAW_ROW
+  jsr print_name
+  pla
+  rts
+
+  ; printing game name on the bottom
+print_last_name:
+  pha
+  lda <LAST_LINE_GAME
+  sta <TEXT_DRAW_GAME
+  lda <LAST_LINE_GAME+1
+  sta <TEXT_DRAW_GAME+1
+  lda <LAST_LINE_MODULO
+  sta <TEXT_DRAW_ROW
+  jsr print_name
+  pla
+  rts
+
+print_name:
+  pha
+  tya
+  pha
+  txa
+  pha  
+  ; is it header lines?
+  lda <TEXT_DRAW_GAME+1
+  bne .not_header ; no
+  lda <TEXT_DRAW_GAME
+  beq .header1
+  cmp #1
+  beq .header2
+  jmp .not_header  
+.header1:
+  jsr draw_header1
+  jmp .end_really_really
+.header2:
+  jsr draw_header2
+  jmp .end_really_really
+.not_header:
+  ; when there are not so many games we need so offset
+  lda <TEXT_DRAW_ROW
+  clc
+  adc games_offset
+  sta <TEXT_DRAW_ROW
+  asl <TEXT_DRAW_ROW ; x2
+  lda <TEXT_DRAW_ROW
+  ; detecting target nametable
+  cmp #LINES_PER_SCREEN
+  bcc .first_screen
+  ; second
+  sec
+  sbc #LINES_PER_SCREEN
+  lsr A
+  lsr A
+  lsr A
+  clc
+  adc #$2C
+  bit $2002
+  sta $2006
+  lda <TEXT_DRAW_ROW
+  sec
+  sbc #LINES_PER_SCREEN
+  asl A
+  asl A
+  asl A
+  asl A
+  asl A
+  sta $2006
+  jmp .print_end
+  ; first
+.first_screen:
+  lsr A
+  lsr A
+  lsr A
+  clc
+  adc #$20
+  bit $2002
+  sta $2006
+  lda <TEXT_DRAW_ROW
+  asl A
+  asl A
+  asl A
+  asl A
+  asl A
+  sta $2006
+.print_end:
+  ; we need to substract 2 from game number
+  lda <TEXT_DRAW_GAME
+  sec
+  sbc #2
+  sta <TEXT_DRAW_GAME
+  lda <TEXT_DRAW_GAME+1
+  sbc #0
+  sta <TEXT_DRAW_GAME+1
+  ; is it footer?
+  lda <TEXT_DRAW_GAME
+  sec
+  sbc games_count
+  lda <TEXT_DRAW_GAME+1
+  sbc games_count+1
+  bcc .print_text_line
+  ldx <TEXT_DRAW_GAME
+  cpx games_count
+  beq .footer1
+  dex
+  cpx games_count
+  beq .footer2
+  jmp .end
+.footer2:
+  jsr draw_footer2
+  ; lets keep for footer text palette, i like how it looks
+  jmp .end
+.footer1:
+  jsr draw_footer1
+  jmp .end
+.print_text_line:
+  lda <TEXT_DRAW_GAME+1
+  jsr select_bank
+  lda #LOW(game_names)
+  clc
+  adc <TEXT_DRAW_GAME
+  sta <TMP
+  lda #HIGH(game_names)
+  adc #0
+  sta <TMP+1
+  lda <TMP
+  clc 
+  adc <TEXT_DRAW_GAME
+  sta <TMP
+  lda <TMP+1
+  adc #0
+  sta <TMP+1  
+  ldy #0
+  lda [TMP], y
+  sta COPY_SOURCE_ADDR
+  iny
+  lda [TMP], y
+  sta COPY_SOURCE_ADDR+1
+  ; spaces on the left
+  ldx #GAME_NAMES_OFFSET+1
+.print_blank:
+  lda #$00
+  sta $2007
+  dex
+  bne .print_blank  
+  ; text
+  ldx #GAME_NAMES_OFFSET+1
+  ldy #0
+  lda #1
+.next_char:
+  cmp #0 ; after zero we are not printing letters but printing spaces
+  beq .end_of_line
+  lda [COPY_SOURCE_ADDR], y
+.end_of_line:
+  sta $2007  
+  iny
+  inx
+  cpx #CHARS_PER_LINE
+  bne .next_char
+.end:
+  ; but if it upper part, we need to erase two lines
+  lda <TEXT_DRAW_ROW
+  cmp #4
+  bcs .end_really
+  ldy #CHARS_PER_LINE
+  lda #0
+.clear_2nd_line:
+  sta $2007
+  dey
+  bne .clear_2nd_line
+.end_really:
+  ; attributes for text
+  lda <TEXT_DRAW_ROW
+  cmp #LINES_PER_SCREEN
+  bcc .print_palette_addr_first_screen
+  ; second nametable
+  lda #$2F
+  sta $2006
+  lda <TEXT_DRAW_ROW
+  sec
+  sbc #LINES_PER_SCREEN
+  jmp .print_palette_addr_select_end
+  ; first nametable
+.print_palette_addr_first_screen:
+  lda #$23
+  sta $2006
+  lda <TEXT_DRAW_ROW
+.print_palette_addr_select_end:
+  ; one byte for 4 rows
+  lsr A
+  lsr A
+  asl A
+  asl A
+  asl A
+  clc
+  adc #$C0
+  sta $2006
+  lda #$FF
+  sta $2007
+  sta $2007
+  sta $2007
+  sta $2007
+  sta $2007
+  sta $2007
+  sta $2007
+  sta $2007  
+.end_really_really:
+  pla
+  tax
+  pla
+  tay
+  pla
+  rts
+
+move_cursors:
+  ; fine cursor scrolling
+  lda <SPRITE_1_X_TARGET
+  cmp SPRITE_1_X
+  beq .sprite_1x_target_end
+  bcs .sprite_1x_target_plus
+  lda SPRITE_1_X
+  sec
+  sbc #4
+  sta SPRITE_1_X
+  jmp .sprite_1x_target_end
+.sprite_1x_target_plus:
+  lda SPRITE_1_X
+  clc
+  adc #4
+  sta SPRITE_1_X
+.sprite_1x_target_end:
+  lda <SPRITE_1_Y_TARGET
+  cmp SPRITE_1_Y
+  beq .sprite_1y_target_end
+  bcs .sprite_1y_target_plus
+  lda SPRITE_1_Y
+  sec
+  sbc #4
+  sta SPRITE_0_Y
+  sta SPRITE_1_Y
+  jmp .sprite_1y_target_end
+.sprite_1y_target_plus:
+  lda SPRITE_1_Y
+  clc
+  adc #4
+  sta SPRITE_0_Y
+  sta SPRITE_1_Y
+.sprite_1y_target_end:
+  rts
+
+  ; fine scrolling to target line
+move_scrolling:
+  ; determining scroll speed
+  lda <SCROLL_LINES
+  clc
+  adc #2
+  sta <TMP
+  lda <SCROLL_LINES+1
+  adc #0
+  sta <TMP+1
+  lda <SCROLL_LINES_TARGET
+  sec
+  sbc <TMP
+  lda <SCROLL_LINES_TARGET+1
+  sbc <TMP+1
+  bcs .move_scrolling_fast_down
+  lda <SCROLL_LINES_TARGET
+  clc
+  adc #2
+  sta <TMP
+  lda <SCROLL_LINES_TARGET+1
+  adc #0
+  sta <TMP+1
+  lda <SCROLL_LINES
+  sec
+  sbc <TMP
+  lda <SCROLL_LINES+1
+  sbc <TMP+1
+  bcs .move_scrolling_fast_up  
+  ; slow scrolling
+  jsr .move_scrolling_real
+  rts  
+  ; fast scrolling
+.move_scrolling_fast:
+  jsr .move_scrolling_real
+  jsr .move_scrolling_real
+  jsr .move_scrolling_real
+  jsr .move_scrolling_real
+  rts
+.move_scrolling_fast_up:
+  jmp scroll_line_up
+.move_scrolling_fast_down:
+  jmp scroll_line_down
+.move_scrolling_real:
+  ; do we need to move screen?
+  ldx <SCROLL_LINES_TARGET
+  cpx <SCROLL_LINES
+  bne .need
+  ldx <SCROLL_LINES_TARGET+1
+  cpx <SCROLL_LINES+1
+  bne .need
+  ldx <SCROLL_FINE
+  bne .need
+  rts  
+  ; we need it
+.need:
+  lda <SCROLL_LINES
+  sec
+  sbc <SCROLL_LINES_TARGET
+  lda <SCROLL_LINES+1
+  sbc <SCROLL_LINES_TARGET+1
+  bcc .target_plus
+  ; scrolling up
+  lda <SCROLL_FINE
+  sec
+  sbc #4
+  bmi .target_minus
+  sta <SCROLL_FINE
+  rts  
+.target_minus:
+  and #$0f
+  sta <SCROLL_FINE
+  jsr scroll_line_up
+  rts    
+.target_plus:
+  ; scrolling down
+  lda <SCROLL_FINE
+  ; adding fine value
+  clc
+  adc #4
+  sta <SCROLL_FINE
+  cmp #16
+  bne .end
+  ; down if fine >=16
+  lda #0
+  sta <SCROLL_FINE  
+  jsr scroll_line_down
+.end:
+  rts
+
+set_cursor_targets:
+  ; set scroll targets first
+.not_ok1:
+  lda <SCROLL_LINES_TARGET
+  clc
+  adc #10
+  sta <TMP
+  lda <SCROLL_LINES_TARGET+1
+  adc #0
+  sta <TMP+1
+  lda <TMP
+  sec
+  sbc <SELECTED_GAME
+  lda <TMP+1
+  sbc <SELECTED_GAME+1
+  bcs .ok1 ; надо скроллить вниз
+  lda <SCROLL_LINES_TARGET
+  clc
+  adc #1
+  sta <SCROLL_LINES_TARGET
+  lda <SCROLL_LINES_TARGET+1
+  adc #0
+  sta <SCROLL_LINES_TARGET+1
+  jmp .not_ok1  
+.ok1:
+.not_ok2:
+  lda <SELECTED_GAME
+  sec
+  sbc <SCROLL_LINES_TARGET
+  lda <SELECTED_GAME+1
+  sbc <SCROLL_LINES_TARGET+1
+  bcs .ok2 ; надо скроллить вверх
+  lda <SCROLL_LINES_TARGET
+  sec
+  sbc #1
+  sta <SCROLL_LINES_TARGET
+  lda <SCROLL_LINES_TARGET+1
+  sbc #0
+  sta <SCROLL_LINES_TARGET+1
+  jmp .not_ok2
+.ok2:
+  ; set cursor targets depending on selected game number
+  ; left cursor, X
+  ldx <SELECTED_GAME
+  lda #GAME_NAMES_OFFSET*8
+  sta <SPRITE_0_X_TARGET  
+  ; right cursor, X
+  lda <SELECTED_GAME+1
+  jsr select_bank
+  ldx <SELECTED_GAME
+  ldy loader_data_cursor_pos, x
+  dey
+  tya
+  clc
+  adc #GAME_NAMES_OFFSET+2
+  asl A
+  asl A
+  asl A
+  sta <SPRITE_1_X_TARGET  
+  ; Y coordinate it the same for both
+  lda <SELECTED_GAME  
+  ; when there are not so many games
+  clc
+  adc games_offset  
+  sec 
+  sbc <SCROLL_LINES_TARGET
+  clc
+  adc #2
+  asl A
+  asl A
+  asl A
+  asl A
+  sec
+  sbc #1
+  .if ENABLE_TOP_OFFSET!=0 ; for large images on top
+  clc
+  adc #8
+  .endif
+  sta <SPRITE_0_Y_TARGET
+  sta <SPRITE_1_Y_TARGET
+  rts
+  
+stars:
+  lda <STAR_SPAWN_TIMER
+  cmp #$E0 ; stars count
+  beq .spawn_end  
+  inc <STAR_SPAWN_TIMER
+  lda <STAR_SPAWN_TIMER
+  and #$0F
+  cmp #0
+  bne .spawn_end
+  lda <STAR_SPAWN_TIMER
+  lsr A
+  lsr A
+  tay
+  lda <STAR_SPAWN_TIMER
+  lda #$FC ; Y, below screen
+  sta SPRITES+4, y
+  iny
+  jsr random ; random tile
+  and #$03
+  clc
+  adc #$71
+  sta SPRITES+4, y
+  iny
+  jsr random  ; attributes, random palette
+  and #%00000011 ; palette - tho lowest bits
+  ora #%00100000 ; low priority bit
+  sta SPRITES+4, y
+  iny
+  jsr random
+  sta SPRITES+4, y
+.spawn_end:
+  ldy #8
+.move_next:
+  lda SPRITES, y
+  cmp #$FF
+  beq .move_end
+  tya
+  lsr A
+  lsr A
+  and #$07
+  cmp #$00
+  beq .move_fast
+  cmp #$01
+  beq .move_fast
+  cmp #$02
+  beq .move_fast
+  cmp #$03
+  beq .move_medium
+  cmp #$04
+  beq .move_medium
+  cmp #$05
+  beq .move_slow
+  cmp #$06
+  beq .move_slow  
+.move_very_slow: ; default
+  lda SPRITES, y
+  sbc #1
+  jmp .moved
+.move_slow:
+  lda SPRITES, y
+  sec
+  sbc #2
+  jmp .moved
+.move_medium:
+  lda SPRITES, y
+  sec
+  sbc #3
+  jmp .moved
+.move_fast:
+  lda SPRITES, y
+  sec
+  sbc #4
+.moved:
+  sta SPRITES, y
+  cmp #$0A
+  bcs .move_next1
+  lda #$FC
+  sta SPRITES, y ; reset Y
+  jsr random  ; random tile
+  and #$03
+  clc
+  adc #$71
+  sta SPRITES+1, y
+  jsr random ; random X
+  sta SPRITES+3, y
+  jsr random ; random attributes
+  and #%00000011 ; palette - lowest tho bits
+  ora #%00100000 ; priority bit
+  sta SPRITES+2, y
+.move_next1:
+  iny
+  iny
+  iny
+  iny
+  bne .move_next  
+.move_end:
+  rts
+
+load_text_palette:
+  lda #$23
+  sta $2006
+  lda #$C8
+  sta $2006
+  lda #$FF
+  ldy #$38
+.print_warning_palette:
+  sta $2007
+  dey
+  bne .print_warning_palette
+  rts
+
+  ; print null-terminated string from [COPY_SOURCE_ADDR]
+print_text:
+  ldy #0
+.loop:
+  lda [COPY_SOURCE_ADDR], y
+  sta $2007
+  iny
+  cmp #0 ; stop at zero
+  bne .loop
+  rts
+
+saving_warning_show:
+  ; disable PPU
+  lda #%00000000
+  sta $2000
+  sta $2001
+  jsr waitblank_simple
+  jsr clear_screen
+  lda #$21
+  sta $2006
+  lda #$C0
+  sta $2006
+  lda #LOW(saving_text)
+  sta COPY_SOURCE_ADDR
+  lda #HIGH(saving_text)
+  sta COPY_SOURCE_ADDR+1
+  jsr print_text
+  jsr load_text_palette
+  jsr waitblank_simple
+  bit $2002
+  lda #0
+  sta $2005
+  sta $2005
+  lda #%00001000
+  sta $2000
+  lda #%00001010
+  sta $2001
+  jsr waitblank_simple
+  rts
+
+saving_warning_hide:
+  lda #%00000000 ; disable PPU
+  sta $2000
+  sta $2001
+  jsr waitblank_simple
+  jsr clear_screen
+  rts