odc2.a48

; Copyright (C) 1997-1999 by Soeren Gust, sgust@ithh.informationstheater.de
; Copyright (C) 2010 by Felipe Corrêa da Sanches, juca@members.fsf.org
; Copyright (C) 2010 by Leandro Lameiro, lameiro@gmail.com
; Copyright (C) 2010 by Niels van Dijkhuizen, niels_van_dijkhuizen@yahoo.com

; This program is free software; you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation; either version 2 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program; if not, write to the Free Software
; Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

	cpu	8048

time_parameter equ 20h
yoffs equ 21h
snow_x0 equ 22h

N1 equ 00h
N2 equ 04h
N3 equ 08h
N4 equ 0ch
N5 equ 10h
N6 equ 14h
N7 equ 18h
N8 equ 1ch
N9 equ 20h
N10 equ 24h
N11 equ 12h

TONE equ 80h
NOISE equ 40h 
PAUSE equ 20h
JUMPTO equ 10h

	org	400h

    include	"bitfuncs.inc"	
	include	"g7000.h"

	jmp	selectgame	; RESET
	jmp	irq		; interrupt
	jmp	timer		; timer
	jmp	vsyncirq	; VSYNC-interrupt
	jmp	start		; after selectgame
	jmp	mysoundirq	; sound-interrupt

timer	retr			; we don't need timer

;calc_cos:
;	input:
;A <-- alpha
;	output:
;A --> 128 + 128*cos(alpha)

calc_sin
	add a,#16*3 ; shift -90 degrees = +270 degrees (64 steps = 2pi radians = 360 degrees)
calc_cos
	anl a, #03fh ;mask-in 6 lower bits (limit to range 0-63)
	add	a,#lo(cos_table)
	movp a,@a
	ret

cos_table
	include	"cos_table.inc"

rewired_str
	db 7
	db _R, _E, _W, _I, _R, _E, _D

_2010_str
	db 4
	db _2, _0, _1, _0

start
	mov r0, #lo(snow_x0)

	mov a, #0
	mov @r0, a
	inc r0

	mov a, #80
	mov @r0, a
	inc r0

	mov a, #30
	mov @r0, a
	inc r0

	mov a, #60
	mov @r0, a

	mov a, #lo(rewired_tune)
	mov a, #76h
	call playsound

main_loop

    call waitvsync

	;increment time time_parameter:
	mov r0,#time_parameter
	inc @r0

	mov r0, #lo(yoffs)
	mov @r0, #0
    mov     r7,#lo(rewired_str)
	call print_string_in_circles

	call print_snowflakes

;-----------------

;routine to wait for the middle of the screen:
	mov r0, #0c0h
here0
	mov r1, #02h
here1
	djnz r1, here1
	djnz r0, here0

;-----------------

	mov r0, #lo(yoffs)
	mov @r0, #80
    mov     r7,#lo(_2010_str)
	call print_string_in_circles

    jmp main_loop

setup_snow_char
	mov r5, #29h	; char "x"
	;is it odd?
	anl a, #04h
	jz odd_time_parameter
	inc r5 			; char "%"
odd_time_parameter
	ret

print_snowflakes
	mov r0,#time_parameter
	mov a,@r0
	mov r1,a; r1 = time_parameter

	mov r0,#vdc_char8
	mov r2,#4; four snowflakes
snowflake
	mov a, r1
	call setup_snow_char

	mov a, r1
	mov r4, a ; y=time_parameter
	call calc_cos

	anl a, #0fch
	rr a
	rr a

	mov r3,a ; x = 30 + 32 + 32*cos(time_parameter*2*pi/64)

	;store copy of R0
	mov a, r0
	mov r7, a

	mov a, r2
	dec a
	add a, #lo(snow_x0)
	mov r0, a
	mov a,@r0

	;add initial x-offset to the calculated x-offset
	add a, r3
	mov r3, a

	;restore R0
	mov a, r7
	mov r0, a

	mov r6, #col_chr_white
	call printchar

	mov a, r1
	add a, #60
	mov r1, a ; different time_parameter for each snowflake	

	djnz r2, snowflake
	ret

;input:
;   R7 <-- string address
;output:
;   NONE
;alters:
;   A (R0) R1 R2 (R3) (R4) R5 R6 R7

print_string_in_circles
	;ret
; read time time_parameter into R1:
	mov r0,#time_parameter
	mov a,@r0

	;speed/4:
	anl a, #0fch
	rr a
	rr a

	mov r1,a ; r1=time_parameter/4

	call	gfxoff

	mov a, r7
	movp a,@a
	mov r2,a
	inc r7

	mov     r0,#vdc_char0
loop
	mov     a,r7
    movp    a,@a
    mov     r5,a
    inc     r7

	mov a, #lo(string_colors)
	add a, r2
	movp a,@a
	mov r6, a

	call calc_char_position

	dec r1
	dec r1
;	dec r1
    call    printchar           ; print it
    djnz    r2,loop             ; do it again

	call	gfxon
	ret

string_colors
	db col_chr_green, col_chr_red, col_chr_white
	db col_chr_green, col_chr_red, col_chr_white
	db col_chr_green, col_chr_red, col_chr_white

;old-colorful pallete
;	db col_chr_violet, col_chr_green, col_chr_red, col_chr_blue, col_chr_yellow, col_chr_cyan
;	db col_chr_violet, col_chr_green, col_chr_red, col_chr_blue, col_chr_yellow, col_chr_cyan

;input:
;   R1 <- alpha
;output:
;	R3 -> x = 8 + 64 + 64*sin(alpha*2*pi/64)
;	R4 -> y = yoffset + 8 + 64 + 64*cos(alpha*2*pi/64)
;alters:
;   A, R3, R4
;
calc_char_position

	;add y offset to char coordinates (double sprites hack)
;	mov r4,r0
	mov a, r0
	mov r4, a

	mov r0, #lo(yoffs)
	mov a, @r0
	mov r3, a

	;mov r0, r4
	mov a,r4
	mov r0,a

	mov a, r3

	mov r4, a ; r4=yoffs

	mov a,r1
	add a,r1
	add a,r1

	call calc_cos
	anl a, #0fch ;mask out lower bits
	rr a; divide by 2
	rr a; divide by 2

	add a, #48 ; add an x offset

	add a, r4; add the initial yoffset
	mov r4,a ;y-coordinate for char

    mov a,r1
	add a,r1

	call calc_sin
	anl a, #0fch
	rr a
	rr a

	add a, #48 ; 8 pixel away from the border

	mov r3,a ;x-coordinate for char
	ret

	org	0700h

mysoundirq
	; check if BIOS sound or custom sound
	mov	a,r4
	add	a,#08ah		; >= 076h
	jc	.custom
	jmp	soundirq	; BIOS tune

.custom	; custom sound handler, read sound opcodes from current page
	mov	a,r4
	movp	a,@a
	mov	r1,a		; command byte
	inc	r4
	xrl	a,#0fh
	jz	.op0f		; test for new opcode
	mov	a,r4
	movp	a,@a
	mov	r2,a		; time_parameter byte
	jmp	parsesnd	; let BIOS sound IRQ handle opcode

	; opcode 0F: sound off, copy next 3 bytes into A7/8/9
.op0f	mov	r0,#vdc_soundctrl
	clr	a
	movx	@r0,a		; old sound off
	mov	r0,#vdc_sound0
	mov	r1,#3		; number of bytes to copy
.loop	mov	a,r4
	movp	a,@a
	movx	@r0,a
	inc	r0
	inc	r4
	djnz	r1,.loop
	jmp	mysoundirq	; restart sound handler


chord macro note1,note2
        db TONE|2, note1
        db TONE|2, note2
        db TONE|2, note1
        db TONE|2, note2
        db TONE|2, note1
        db TONE|2, note2
        endm

noise macro length
	db NOISE|length, 0FFh
	endm

	org 776h

rewired_tune

        db TONE|12,N1
        db PAUSE|4
	noise 3
	db PAUSE|3
        db TONE|10,N2
        db PAUSE|8
	noise 3
        db PAUSE|9
        db TONE|10,N2
        db PAUSE|8
        noise 3
        db PAUSE|9

;----2

        db TONE|12,N1
        db PAUSE|4
        noise 3
        db PAUSE|3
        db PAUSE|10
        db TONE|10,N2
        db PAUSE|8
        noise 3
        db PAUSE|9
        db TONE|10,N4
        db PAUSE|8
        noise 3
        db PAUSE|9
;----3

        chord N6,N7
        db PAUSE|4
        noise 3
        db PAUSE|3
        db TONE|10,N2
        db PAUSE|8
        noise 3
        db PAUSE|9
        db TONE|10,N2
        db PAUSE|8
        noise 3
        db PAUSE|9
;----4

        chord N4,N5
        db PAUSE|4
        noise 3
        db PAUSE|3
        db TONE|10,N2
        db PAUSE|8
        noise 3
        db PAUSE|9
        db TONE|10,N2
        db PAUSE|8
        noise 3
        db PAUSE|9

;----
	db JUMPTO, lo(rewired_tune)