( dev/audio )

%MOD { DUP2 DIV MUL SUB }

(
	position in track, 
	frame: counter for current frame, 
	only playing every few frames 
)

@timer $1
@progress $1

( devices )

|00 @System     [ &vector $2 &pad    $6 &r      $2 &g     $2 &b      $2 ]
|20 @Screen     [ &vector $2 &width  $2 &height $2 &pad   $2 &x      $2 &y    $2 &addr  $2 &color $1 ]
|30 @Audio     	[ &wave $2   &env    $2 &pad    $4 &vol   $1 &pitch  $1 &play $1 &value $2 &delay $2 &finish $1 ]

|0100 ( -> )
	
	( set color pallete )
	#00ff .System/r DEO2 
	#0f0f .System/g DEO2 
	#0ff0 .System/b DEO2 

	;on-frame .Screen/vector DEO2 ( run on-frame every 1/60th of a second )
	#ff .Audio/vol DEO            ( set volume to max )
	;saw .Audio/wave DEO2         ( set waveform to saw for audio engine )
	;env .Audio/env DEO2          ( set envelope for audio engine )

BRK

@on-frame ( -> )

	( incr ) .timer PEK #01 ADD .timer POK 
	( skip ) .timer PEK #10 EQU ,&play-note JNZ BRK &play-note

	( get note )
	;melody #00 .progress PEK ADD2 GET ( -- note )

	( play note )
	DUP #80 ORA .Audio/pitch DEO ( -- note ) ( OR note with #80 and set the audio pitch to it. )
	#01 .Audio/play DEO ( play the note )

	( erase last note )
	#20  .Screen/color DEO ( draw a dot )

	( draw note )
	#00 SWP #0004 MUL2 #0100 SUB2 .Screen/y DEO2 ( calculate the y position of a dot. TODO make this not upside down )
	#00 .progress PEK #0008 MUL2 .Screen/x DEO2 ( calculate the x position of a dot )
	;dot .Screen/addr DEO2 ( set the sprite for a dot )
	#21  .Screen/color DEO ( draw a dot )

	( incr ) .progress PEK #01 ADD #20 MOD .progress POK

	#00 .timer POK

BRK

@silence ( -> )

BRK

( defines a sawtooth wave. )

@saw ( -> )

	#6000 .Audio/value DEO2
	#0000 .Audio/delay DEO2 ( move to volume #600 after 0 delay )
	#0000 .Audio/value DEO2
	#ffff .Audio/delay DEO2 ( reach volume 0 after the whole note. Interpolated linearly )

BRK

( defines an envelope )

@env ( -> )

	#ffff .Audio/value DEO2
	#1000 .Audio/delay DEO2 ( move pretty quickly to volume #ffff (maximum) ) 
	#0000 .Audio/value DEO2
	#4000 .Audio/delay DEO2 ( interpolating linearly, move to #0000 after a delay of #4000 where #8000 is half a second )
	#00   .Audio/finish DEO ( end the envelope )

BRK

( song data, #ff is used for a rest )

@melody [ 
	54 52 54 4f 4b 4f 48 ff
	54 52 54 4f 4b 4f 48 ff
	54 56 57 56 57 54 56 54 
	56 52 54 52 54 50 54 ff
] 

( dot sprite )
	 
@dot [ 003c 7eff 7e3c 0000 ]