/*                |                     |    o
   ,---.,   ..   .|__/ ,---.,--.--.,---.|--- .,---.
   |   ||   ||   ||  \ |   ||  |  |,---||    ||
   `   '`---|`---'`   ``---'`  '  '`---^`---'``---'
        `---'              :.by..stardust..2025.:   */

; default org = $6000 (any address within $6000..$ff00 is fine)
; esc: toggle editor | f1: options | f5: recompile | f12: reset

	org $6000
	
loop	ld hl, $5800
	ld de, $5801
	ld bc, 767
	ld a, 1
	and 7
	out ($fe), a
	.3 add a
	ld (hl), a
	ldir
	
	ld hl,$0000 
	ld de,$4000
	ld bc,$1800
	ldir	
	
	ld hl,$4000
	ld de,$5800
	ld b,200
l2	ld (hl),a 
	ld a,(number)
	out ($fe),a
	.2 inc a
	ld (number),a
	.30 inc hl
	
	out ($fe),a

	ld c,32
	ld hl,(adr)
	ld de,(adr2)
l0	ld (hl),a
	ld (de),a
	inc hl
	inc de
	.12 inc a
	dec c
		
	jr nz,l0
	
	ld b,11
	ld hl,(llll)
	ld a,%11001101
l90	ld (hl),a
	inc hl
	inc hl
	djnz l90		
		
	djnz l2	
 	
	jr loop


number  db 34

adr	dw $5800 + 32*1
adr2	dw $5800 + 32*22

llll	dw $5800 + 32*11 + 5

;----------------------------------------
; Snippets:
;  down_hl
;  up_hl
;  hl_to_scr
;  scr_to_attrs
;  set_point
;  rnd16
;  gen_sin
;----------------------------------------

;----------------------------------------
; Next screen line address in HL
;----------------------------------------
down_hl
	inc  h
	ld   a, h
	and  #07
	ret  nz
	ld   a, l
	sub  #e0
	ld   l, a
	sbc  a
	and  #f8
	add  h
	ld   h, a
	ret

;----------------------------------------
; Previous screen line address in HL
;----------------------------------------
up_hl
	dec  h
	ld   a, h
	cpl
	and  #07
	ret  nz
	ld   a, l
	sub  #20
	ld   l, a
	ret  c
	ld   a, h
	add  #08
	ld   h, a
	ret

;----------------------------------------
; in:  L = x [0..255]
;      H = y [0..191]
; out: HL = addr in screen [4000..57FF]
;      C = pixel number [0..7]
;----------------------------------------
hl_to_scr
	ld   c, l
	ld   a, l
	.3   rlca
	xor  h
	and  #c7
	xor  h
	.2   rlca
	ld   l, a
	ld   a, h
	and  #c0
	inc  a
	.3   rra
	xor  h
	and  #f8
	xor  h
	ld   h, a
	ld   a, c
	and  7
	ret

;----------------------------------------
; in:  HL = addr in screen [4000..57FF]
; out: HL = addr in attrs [5800..5AFF]
;----------------------------------------
scr_to_attrs
	ld   a, h
	.3   rrca
	and  #03
	or   #58
	ld   h, a
	ret

;----------------------------------------
; in:  L = x [0..255]
;      H = y [0..191]
;----------------------------------------
set_point
	call hl_to_scr
	ld   de, pixel_tbl
	add  e
	ld   e, a
	ld   a, (de)
	ld   (hl), a
	ret

	align 8
pixel_tbl
	db #80,#40,#20,#10,#08,#04,#02,#01

;----------------------------------------
; in:  none
; out: HL = random 16bit value
;----------------------------------------
rnd16
.sd	equ  $+1
	ld   de, 0
	ld   a, d
	ld   h, e
	ld   l, 253
	or   a
	sbc  hl, de
	sbc  a, 0
	sbc  hl, de
	ld   d, 0
	sbc  a, d
	ld   e, a
	sbc  hl, de
	jr   nc, .st
	inc  hl
.st	ld  (.sd), hl
	ret

;----------------------------------------
; in:  IX = addr of 256b buffer
; out: generated sin table
;----------------------------------------
gen_sin
	ld   de, #7fbc
	ld   hl, #ff7f
.g0	ld   a, d
	xor  #80 ; uncomment for unsigned
	ld   (ix), a
	xor  #80 ; uncomment for unsigned
	rla
	sbc  a
	ld   b, a
	ld   c, d
	adc  hl, bc
	rr   c
	rrca
	rr   c
	add  hl, bc
	ld   b, h
	ld   a, l
	ex   de, hl
	sra  b: rra
	sra  b: rra
	sra  b: rra
	ld   c, a
	; or   a
	sbc  hl, bc
	ex   de, hl
	inc  ixl
	jr   nz, .g0
	ret