nuclear@0: ; vi:ft=rgbasm:
nuclear@0: include "hw.inc"
nuclear@0: 
nuclear@0: xoffs_center equ 4
nuclear@0: yoffs_center equ 12
nuclear@0: 
nuclear@0: frame_ptr equ $ff80
nuclear@0: 
nuclear@0: section "hdr", ROM0[$100]
nuclear@0:         nop
nuclear@0:         jp main
nuclear@0: 
nuclear@0: rept $150 - $104
nuclear@0:         db 0
nuclear@0: endr
nuclear@0: 
nuclear@0: section "text", ROM0
nuclear@0: 
nuclear@0: main:
nuclear@0: 	call init
nuclear@0: 
nuclear@0: 	xor a, a
nuclear@0: 	ldh [frame_ptr], a
nuclear@0: .mainloop:
nuclear@0: 	ldh a, [REG_LY]
nuclear@0: 	cp a, 144
nuclear@0: 	jr c, .wait_hsync
nuclear@0: 
nuclear@0: 	; we're in vsync, increment frame counter and wait for the next frame
nuclear@0: 	ldh a, [frame_ptr]
nuclear@0: 	inc a
nuclear@0: 	ldh [frame_ptr], a
nuclear@0: .wait_newframe:
nuclear@0: 	ldh a, [REG_LY]
nuclear@0: 	cp a, 0
nuclear@0: 	jr nz, .wait_newframe
nuclear@0: 
nuclear@0: 	; scanline code
nuclear@0: .wait_hsync:
nuclear@0: 	ldh a, [REG_STAT]
nuclear@0: 	and a, STAT_MODE_MASK
nuclear@0: 	jr nz, .wait_hsync
nuclear@0: 
nuclear@0: 	ldh a, [frame_ptr]
nuclear@0: 	ld d, a
nuclear@0: 
nuclear@0: 	xor a, a
nuclear@0: 	ld b, a
nuclear@1: 
nuclear@0: 	ldh a, [REG_LY]
nuclear@1: 	add a, d	; add frame number
nuclear@0: 	ld c, a
nuclear@0: 
nuclear@0: 	ld hl, sintab
nuclear@1: 	add hl, bc	; hl now points to the sine value
nuclear@0: 
nuclear@1: 	ld a, [hl]
nuclear@1: 
nuclear@1: 	; add a half-octave sine
nuclear@1: 	ld e, a		; save first sine to e
nuclear@1: 	sla d
nuclear@1: 	ld a, [REG_LY]
nuclear@1: 	sla a
nuclear@1: 	add a, d
nuclear@1: 	ld c, a
nuclear@1: 	srl d
nuclear@1: 
nuclear@1: 	ld hl, sintab
nuclear@1: 	add hl, bc
nuclear@1: 	ld a, [hl]
nuclear@1: 	sra a
nuclear@1: 	add a, e	; add previously saved sine
nuclear@1: 
nuclear@1: 	add a, yoffs_center
nuclear@0: 	ldh [REG_SCY], a
nuclear@0: 
nuclear@1: 	; do something for SCX too
nuclear@1: 	ld a, d
nuclear@1: 	sla a
nuclear@1: 	ld d, a
nuclear@1: 
nuclear@1: 	ldh a, [REG_LY]
nuclear@1: 	add a, 32
nuclear@1: 	add a, d	; add frame number
nuclear@1: 	ld c, a
nuclear@1: 
nuclear@1: 	ld hl, sintab
nuclear@1: 	add hl, bc
nuclear@1: 
nuclear@1: 	ld a, [hl]
nuclear@1: 	sra a
nuclear@1: 	add a, xoffs_center
nuclear@1: 	ldh [REG_SCX], a
nuclear@1: 
nuclear@0: 	; done, wait until we're out of hsync
nuclear@0: .wait_endhsync:
nuclear@0: 	ldh a, [REG_STAT]
nuclear@0: 	and a, STAT_MODE_MASK
nuclear@0: 	jr z, .wait_endhsync
nuclear@0: 
nuclear@0: 	jr .mainloop 
nuclear@0: 
nuclear@0: 
nuclear@0: 	di
nuclear@0: .end:   halt
nuclear@0:         nop
nuclear@0:         jp .end
nuclear@0: 
nuclear@0: init:
nuclear@0: 	call wait_vsync
nuclear@0: 	xor a, a
nuclear@0: 	ldh [REG_LCDC], a
nuclear@0: 
nuclear@2: 	; setup palette
nuclear@0: 	ld a, $1b
nuclear@0: 	ldh [REG_BGP], a
nuclear@0: 
nuclear@0: 	; copy tiles
nuclear@0: 	ld hl, $8000
nuclear@0: 	ld de, tiles
nuclear@0: 	ld bc, tiles_end - tiles
nuclear@0: .copytiles:
nuclear@0: 	ld a, [de]
nuclear@0: 	ld [hl+], a
nuclear@0: 	inc de
nuclear@0: 	dec bc
nuclear@0: 	ld a, b
nuclear@0: 	or c
nuclear@0: 	jp nz, .copytiles
nuclear@0: 
nuclear@0: 	; copy tilemap
nuclear@0: 	ld hl, $9800
nuclear@0: 	ld de, tilemap
nuclear@0: 	ld b, 21
nuclear@0: .copymap:
nuclear@0: 	ld c, 21
nuclear@0: .copymaprow:
nuclear@0: 	ld a, [de]
nuclear@0: 	inc de
nuclear@0: 	ld [hl+], a
nuclear@0: 	dec c
nuclear@0: 	jr nz, .copymaprow
nuclear@0: 
nuclear@0: 	push bc
nuclear@0: 	ld bc, 11
nuclear@0: 	add hl, bc
nuclear@0: 	pop bc
nuclear@0: 
nuclear@0: 	dec b
nuclear@0: 	jr nz, .copymap
nuclear@0: 
nuclear@0: 	; center viewport
nuclear@0: 	ld a, yoffs_center
nuclear@0: 	ldh [REG_SCY], a
nuclear@0: 	ld a, xoffs_center
nuclear@0: 	ldh [REG_SCX], a
nuclear@0: 
nuclear@0: 	; configure LCD
nuclear@0: 	ld a, LCDC_DISPON | LCDC_CHAR_8000 | LCDC_BGON
nuclear@0: 	ldh [REG_LCDC], a
nuclear@0: 	ret
nuclear@0: 
nuclear@0: wait_vsync:
nuclear@0: 	ldh a, [REG_LY]
nuclear@0: 	cp a, 144
nuclear@0: 	jr c, wait_vsync
nuclear@0: 	ret
nuclear@0: 
nuclear@0: section "data", ROM0, align[8]
nuclear@0: sintab:
nuclear@0: include "sin.inc"
nuclear@0: 
nuclear@0: tiles:
nuclear@0: incbin "logo.tiles"
nuclear@0: tiles_end:
nuclear@0: tilemap:
nuclear@0: incbin "logo.tilemap"
nuclear@0: tilemap_end: