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282 lines
8.5 KiB
Plaintext
282 lines
8.5 KiB
Plaintext
Another / Out-of-This World Demake for Apple II+
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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by Vince "Deater" Weaver (vince@deater.net)
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http://www.deater.net/weave/vmwprod/ootw/
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Disk and LZ4 routines by qkumba
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+ The game "Another World" was released in 1991.
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Written by Eric Chahi.
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It was eventually ported to many systems (I played it on IBM PC).
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It even got an Apple IIgs port (the IIgs is 16-bit with fancy
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graphics and sound). However you couldn't play it on
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earlier Apple II systems... until now.
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+ I was inspired to do this by this amazing PICO-8 version of:
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https://liquidream.itch.io/another-world-survival
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and thought the Apple II lo-res palette (15 colors, 40x48 graphics)
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might be just barely enough to do it justice.
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==================
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Game controls:
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==================
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This info appears while loading too, but if you are in an emulator with
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fast disk access it might not be on the screen long enough to see.
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D -> - move right (twice to run)
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A <- - move left (twice to run)
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W up - jump
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S down - crouch / pickup
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space - kick / gun
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L - charge weapon
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During the intro, you can press R to make it repeat forever.
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Hints for those who have never actually played the original game:
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+ At initial arrival, hit up a bunch of times to escape the
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tentacle monster. On an original II w/o autorepeat
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you might have to bang on the keyboard a lot.
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+ You can kick some enemies. Crouch-kicking is sometimes
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a bit easier than stand-kicking.
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+ When running (i.e. after pressing left or right twice)
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you can press "up" to run-jump which is faster than
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plain running. That might be useful if you need
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to out-run something.
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+ When you get the gun, use space to fire the laser.
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You can use "L" to charge your gun for special actions.
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Charge a little bit then press "L" (or any key)
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to create a shield.
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Charge a longer time (a few seconds, when the charge
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ball gets bigger) and it will make a giant blast capable
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of destroying doors and shields.
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Note: the original Apple II had no up/down buttons, which is why
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you can also use WASD for movement. Different emulators handle
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this differently, but if for some reason up/down is not working
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try using W/S instead.
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Joystick support: none yet?
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It should be possible, I just haven't had time to implement yet.
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Keyboard Limitations:
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Note, Apple II has simplistic keyboard support.
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In general it's not possible to read more than one key at a time.
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Additionally, on older models there's no auto-repeat unless you
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hold down the REPT key, which makes running difficult.
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This means it's really not possible to use the keyboard the
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same way as the original game (which had you do things
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like holding down spacebar to charge the gun and then
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firing when you release it. Same for running faster
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by holding left/right and space at the same time).
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==================
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Development notes:
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==================
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Ootw Memory map:
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00 zero page
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01 stack
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02 disk-filename (30 bytes)
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03 nibble table/disk data
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04-07 GR page0
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08-0b GR page1
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0c-0f background ($c00 = disk load buffer)
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10-13 background overlay
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14-16 loader
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17-bf program-data (41.25k)
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bc-bf earthquake background (shifted)
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c0-cf I/O
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d0-ff ROM
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Intro Memory map:
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00 zero page
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01 stack
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02 disk filename (30 bytes)
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03 nibble table/disk data
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04-07 GR page0
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08-0b GR page1
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0c-0f offscreen data ($c00 = disk load buffer)
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10-13 offscreen data2
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14-16 loader
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17-89 program/compressed-data (30.25k)
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90-bf currently decompressed level data (12k)
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c0-cf I/O
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d0-ff ROM
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Intro Memory squeeze!
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10,748 over all graphics in
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10,734 over remove extraneous blank bg image
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8,658 over re-arrange memory map, 42k avail now
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8,562 over move gr_make_quake out of common code
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8,374 over remove extraneous code (mostly put_sprite_flipped)
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5,469 over allow changing bg on fly in sequence
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4,122 over modify cyan frames to be on fly
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2,749 over do same for zappo routines
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2,493 over squish disk loader vars to page 3
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2,165 over horrible hack to auto-go to next image in sequence
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2,114 over move bg loading into seq
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2,053 over make elevator indicator a loop
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1,347 over use LZ4 instead of RLE
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Gave up, see if we can compress in chunks and decompress, sort of like
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my chiptune player does.
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Let's take a 12k region of memory = $3000
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$C000 - $3000 = starting at $9000
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ID1 = 1461 2143\
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ID2 = 1759 2687|--- together in 01
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ID3 = 1195 1879/
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ID4 = 2514 8280\--- in 04
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ID5 = 1947 3492/
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ID6 = 2584 3610\ --- in 06
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ID7 = 2834 3606/
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ID8 = 3705 4918 | -- in 08
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ID9 = 4494 5901\ -- in 09
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ID10 = 3397 5558/
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===== ======
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25890 12k
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ootw memory squeeze:
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after full rope sequence in: 23065
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make transparent overlays: 13971
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add end-of-l1 cutscene: 26464
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make transparent overlays: 17821
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add in rest of end cutscene 23906
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make those transparent 21236
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ootw2 memory squeeze:
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before intro 3872
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after intro 9234
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LOADER=1400 TITLE=1.75k = 7 pages = load at $D00
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2560 max size allowed
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L2 Memory map:
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00 zero page
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01 stack
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02 disk-filename
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03 nibble table/disk data
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04-07 GR page0
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08-0b GR page1
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0c-0f offscreen data ($c00 = disk load buffer)
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10-13 offscreen data2
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14-16 loader
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17+ game
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c0-cf I/O
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d0-ff ROM
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since there seems to be vague interest in this, reasons to use the
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various graphics modes.
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lores benefits:
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+ 40x48, 15 colors (two greys) (which is fine, as I use one for sprite transparency)
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+ hardware page flipping
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+ each display only 1kB (leaving lots of room for code) (also fast to clear screen)
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+ (software) sprites and animations are relatively small
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lores downsides:
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+ blocky
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+ pixels are rectangular
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+ framebuffer is non-linear (to get to next line requires a lookup table, not a simple add)
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+ odd/even lines are high/low nibble in a byte, so to draw sprites properly need a lot of shifting an masking (I cheat and only allow sprites on even lines)
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+ framebuffer has "memory holes" between lines. These are areas of memory reserved for expansion card use, so you can't just load a 1kB image straight to the framebuffer as it could break things.
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+ NTSC artifact fringing between colors
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+ lores PAGE2 is not frequently used so is broken in some emulators and on some early IIgs models
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hires benefits:
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+ 140x192 6 colors
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+ hardware page flipping
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hires downsides:
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+ non-linear framebuffer even worse than lo-res
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+ 8kB per page. two pages of hires takes 1/3 of total RAM in an Apple II+
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+ NTSC artifact color. If the bit patterns in adjacent pixels is 00 it makes black, 11 makes white, so if you join two different colors you get lines between them
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+ you get 7 pixels per 2-bytes. Which means a lot of dividing by 7, slow on 6502
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+ each 3.5 pixels has a bit indicating palette (black,white,green,purple) or (black,white,orange,blue). You get zx-spectrum like color clash if you try to mix colors too close together
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+ to get fast software sprites usually you make a set of 7 pre-shifted versions of the sprites, which takes up a lot of room
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double-lores
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+ 80x48, 15 colors
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+ requires IIe or newer (80 column card)
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+ requires drawing extra 1kB of data to bank-switched AUX RAM
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+ AUX ram colors are shifted one bit to left from main bank colors
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+ while it's possible to get hardware page flipping, it's really complex
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double-hires
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+ 140x192, 15 colors!
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+ requires IIe or newer and 128k of RAM
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+ requires drawing 8k of additional data to bank-switched AUX RAM
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+ again, page flipping is complex
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In any case, I chose lo-res for the Another World conversion for 3 reasons
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1. Another World traditionally has 16 colors (and I like the lo-res colors)
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2. I wanted to fit levels in 48k, and as many as possible on a 140k disk
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3. I am too lazy to implement a full hi-res sprite library
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The recent C64 Another World conversion looks much more impressive and hi-res,
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but I think they use a 1MB cartridge just for the intro movie alone
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(which is possible larger than the size of the original game for the Amiga).
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DISK:
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~~~~~
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DISK1:
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TITLE 2540 10s 0T10S T1
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INTRO 35049 137s 8T9S T2..T10
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OOTW_C1 24094 95s 5T15S T11-T16
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OOTW_C2 31845 125s 7T13S T17-T24
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OOTW_C3 3420 14s 0T14S T25
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OOTW_C4 15643 62s 3T14S T26-T29
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OOTW_C5 10333 41s 2T9S T30-T32
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====
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484s = 121k
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DISK2:
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TITLE 2540 10s 0T10S T1
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OOTW_C6 9605 38s 2T6S T2-T4
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OOTW_C7 9704 38s 2T6S T5-T7
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OOTW_C8 9823 39s 2T7S T8-T10
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OOTW_C9 9646 38s 2T6S T11-T13
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OOTW_C10 9646 38s 2T6S T14-T16
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====
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201s = 50k
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DISK3:
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TITLE 2540 10s 0T10S T1
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OOTW_C11 9643 38s 2T6S T2-T4
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OOTW_C12 9707 38s 2T6S T5-T7
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OOTW_C13 9828 39s 2T7S T8-T10
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OOTW_C14 9749 38s 2T6S T11-T12
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OOTW_C15 24658 97s 6T1S T13-T19
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ENDING 22899 90s 5T10S T20-T25
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====
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350 = 87.5k
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