                         Still Alive for the Apple II
                               in roughly 16k

                           By Deater (Vince Weaver)
					vince@deater.net

BACKGROUND
~~~~~~~~~~
	A few years back I implemented Valve's Portal in Applesoft BASIC.

	At the end it played Still Alive, but in horrible single-channel
	speaker beeps.  I always wanted to have this sound better.

	So here is the end result.  Still Alive in 6-Channel Mockingboard
	Sound in 80 column with cursor effects.  Also in 40 column if
	your display can't handle 80 cols.  And if you don't have a
	Mockingboard, then a simpler version using P. Lutus'
	Electric Duet 2-channel audio for the stock speaker.



Fun fact:
	The letter 'Z' does not appear at all in the lyrics to the song.
	(Noticed when I had to edge comparison for uppercase off by one)

Challenges:
	+ 6-channel audio.  Really its 4-channel (from a MOD file)
		but it actually does load and play audio on all 6 channels.
	+ Fitting it all in 48k (want to avoid disk routines if can)
	+ Printing the ASCII art (naive implementation takes longer than 50Hz)
		The ASCII art is roughly 7k.  Thought of decompressing
		on the fly, but the LZ4 code is not re-entrant and
		the music is already decompressing on the fly.
	+ Re-using the Lyrics for both the Mockingboard and Electric Duet
		versions.
	+ Squeezing the compressed image into memory leaving room for
		all the code to be decompressed while leaving enough
		room that DOS still has room to load things.  It's
		an *extremely* tight fit.
	+ An odd issue where the 80col display would get corrupted
		if we set HIRES without explicitly setting LORES
		before doing PR#3


Goal: Binary fits in 16k (16384 bytes)

note						size (bytes)
---------------------				------
initial music player:				 2078
add raw ascii art:				 9142
add 3-channel music+lyrics,then slim a bit:	18787
initial 40 col support:				18864
have art loading properly 40col:		18910
lz4 encode the ascii art:			15529
revert because lz4 code not re-entrant:		18910
add 4-channel music (KR4):			20128
add cursor (a bit distracting):			20162
feature complete 40 col:			20180
intial 80 col support:				20191
80 col cursor:					20344
strip out some unneeded text printing:		19962
merge ED and MB code:				24993
properly select between versions:		25001
merge the ED and MB lyrics:			22828
80 column ED, wait for keypress+reboot at end:	22852
Crazy compression:
Remove mockingboard detection:			16343

Memory Map:



0000:		Zero Page
0100:		Stack
0400:		Text Page 0 (AUX 0400: 80 column text)

2000:		HGR Page0
4000:		HGR Page1
9600:		DOS		37.5k
C000:		I/O Space
D000:		ROM
FFFF:		END


Plan:
	Load compressed 16k image ($4000) at $5900 - $9900
		We use MAXFILES 1 to give us some extra room
		just before DOS

	Decompress ENDING sequence at $1800 - $4000
		(writes background to HGR graphics automatically)

	STILL_ALIVE:
		+  $0800 - $5900 
			$2e2d of code
			$2282 of KR4 music *or*
			$0842 of ED music 
		+  Sound buffers ($3800, 14k) at $5e00 - $9600

