Building and Linking a new front end to a SEUCK game
Have you ever
written a good SEUCK game, and you get fed up with the same old front
end, with the rolling raster bars?. Or do you want to make more of a
better presentation for a SEUCK game? You can, but before you can
actually do that you may need to learn 6502 assembly to adapt better
features to your presentations.
This tutorial will show you the basics of writing a simple front end
for your own SEUCK game, which will feature a bitmap logo, a 1 screen
presentation and scroll text and of course playing music in the
background. This example will
work on BOTH standard and the SIDEWAYS SEUCK mod. In this example, I'm
going to use one of the existing games called "Grayhawk" by Alf Yngve.
We have also supplied some PD tools for you as well as the example
source code on this disk. If you would like to try it out. Click on the
Disk icon to download it.
You will require the TASM/Codenet cartridge plugin or 1541Ultimate II
with TASM/Codenet set up. Or use of a Cross platform Assembler/Compiler
that supports Binary files.
Or, how about the ACME cross assembler PRG binaries and source? Here
Before you get started, you will need the following
resources set up for the project. I shall also give you tips on various
parts in the tutorial.
- 1541 Ultimate 2 with TASM / CodeNET setup as main cartridge (You can
use WinVice V2.23 or higher using X64SC with a Retro Replay cart Tasm
- A Character Set
- A bitmap picture / logo (Maximum rows 8/9 chars)
- Front end text screen + colour data
- A SEUCK game of your choice (HAHAHA, yes it would be no use otherwise
DESIGN A CHARACTER SET - OR RIP ONE
Your character set can be extracted from your SEUCK, using the M/C
monitor on any freezer cartridge (or VICE monitor). The SEUCK game
front end charset lies from $f400-$f800.
- Press the FREEZE button on the cartridge (or VICE plugin using ALT+Z)
then type in:
You can then load in any Public Domain char editors to update the
characters, put them in place etc. And save them again. Or
alternatively, if you really wanted to. Build your own character set
and save it.
STRIPPING A BITMAP LOGO
A bitmap logo can be saved in different formats, but the common
method I use is to convert an existing bitmap picture into VIDCOM paint
format, and then strip out the picture data file separately.
- Load in a painting program or picture viewer that supports the format
of your picture (E.G. Amica Paint and Interpaint supports Koala Paint
- Display the picture and then press the FREEZE button (ALT+Z if using
VICE). Enter the Picture Save option in the menu and save as VIDCOM
paint format. Enter the filename.
- After saving, press the RESET button and select to enter the FASTLOAD
- Type MON to enter the machine code monitor then enter
L "B.name of picture",8
The Vidcom paint picture data will load from $5800-$7f40. We will need
to strip the data out. Since the logo should be at leat 8 or 9 char
rows. We can strip out a small area of the bitmap data.
- Using the M/C monitor save each part of the picture data separately
using the following:
S "COLOUR RAM",8,5800,5BE8
S "VIDEO RAM",8,5C00,5FE8
OH KRAP - LET'S MAKE PRESENTATION
LINES FOR OUR FRONT END
We want to design / edit our own front end screen text with
colour built in memory. There are different ways in which this could be
done, either find an existing colour+screen editor, or program a small
simple screen+colour editor for personal use. For this one, we are
going to build a little tool called
KRAPSCREEN using the TASM/CodeNET Turbo Assembler utility.
- Press the RESET button (Alt+R) to enter the reset menu and select the
- Type MON and Load in your new/updated charset using the L prompt:
- After loading the charset type in X to exit the monitor
- Type in TASS - This will take you to the Turbo Assembler.
- Now enter the following listing.
*= $0900 ;SYS 2304 to execute
jsr $e544 ;Clear screen
lda #$00 ;Black screen
lda #$18 ;Charset at $2000
sta $d018 ;stored to Char RAM
ldx #$00 ;Cursor Ðosition X
ldy #$00 ;Cursor Ðosition Y
jsr $fff0 ;Store cursor pos
jsr $a560 ;BASIC input
the edited screen to memory ;at
$7c00-$7fe8 and charset colour ;memory
to $8000-$83e8 for SEUCK
ldx #$00 storescr
lda $0400,x ;Screen RAM
sta $7c00,x ;Screem RAM new loc
lda $d800,x ;Colour RAM old loc
sta $8000,x ;Colour RAM new loc
inx ;Loop 256 times
- After typing in the listing press
the BACK ARROW char key (Not cursor right) and 5 to assemble to disk.
The filename can be called "KRAPSCREEN", as it is just a basic screen
editor for this purpose. Not to mention, naff as well :)
- After the program has assembled to disk. Press the RESET button on
the cartridge (ALT+R in VICE). Enter the fastload prompt and load in
- Type new. Enter SYS 2304 to run Krapscreen. Now edit your own front
end screen and colour text. Pressing RETURN will exit KRAPSCREEN with a
- Enter the M/C monitor, by typing in MON
- We shall now save the new front end on screen text. It is already
stored in memory where we want it to be located ($7c00-$83e8). Now
let's save the front end text screen and colour data to disk.
Okay, job is done. Now for the next task.
LET'S MOVE TO THE GROOVE
The next step is to pick some music. You could always browse
through the HVSC for any tunes that Init $1000 and Play $1003 and is
not bigger than $1000 bytes. The bad news is that you will need to
relocate your music to $9000. There are different possible ways.
However, to play it safe, you can use my tunes from my DMC collection
and make use with the All Round Relocator, which can relocate music
composed with JCH Newplayer or DMC V2.0 - DMC V5.1. I included
the relocator with the first two DMC Collections, which available to
download from the C64 Music section on my web site.
- Load in All Round Relocator
- Load in a DMC V4 tune from my collection (Or whatever)
- Relocator should find PLAYER: DMC V4.0, now enter $9000 as the
address where music should relocate to.
- Save the tune.
Alternatively, you could use a PC command line tool called SidReloc,
which will relocate a SID tune saved in PSID form, and relocate it to
another address. For example, say you wanted to relocate a SID tune of
mine called CYBER_TECHNOLOGY.SID. You would need to save it as a PSID
file where SIDRELOC lies and then in the command prompt type in:
Play the tune in SIDPLAY and then extract the tune in PRG / DAT form
and import it into your disk or D64
IT AND SEE
Load in your SEUCK game, which you want to build a new
front end for. Then run it (Unless your game was saved as FINISHED
game, instead of compressed or frozen). Have a little play around with
the game, if you want. Otherwise go into the FREEZE option and enter
the M/C monitor. We want to do some spring cleaning by filling wasted
memory between $6580 - $b6c0 with zero bytes ($00).
- Enter as follows:
6580 B6C0 00
Ok, that was cleaned pretty successful.
- Now let's fix something else in SEUCK. Random firing. Enter as
$54EF LDA $5000,Y
- Ok, nearly done. Just one more thing to add.
Now we're happy with this. Let's load in the data from the M/C monitor
to specified areas
Right, since all is loaded. Lets save it as a whole chunk of data, just
incase something gone wrong somewhere
Assuming that you have got all the data you need and you
had enough, playing the game. It is time to program the new front end
using the Turbo Assembler, in TASM/CodeNET. Where you are still at the
game, press the RESET button (ALT+R in VICE), then enter
TASM/CODENET. Here is the full listing for you to type into the
assembler. I have also included some explanations about what happens in
the code. This is a possible way to build a new front front end and
link it to a SEUCK game.
With new Front End ;by
Richard Bayliss ; ;This
source will call a routine which ;will
skip the standard front end from ;SEUCK
and jump straight on to the new ;front
*= $0810 ;Start address for
part of the code (at $0810) will ;set
the low and high bytes of the new ;front
end, and will force the old ;front
end to JUMP directly to the new ;front
next bit of code will allow use ;of
the high memory area, so if we ;need
to - restore the SEUCK status ;font
(Otherwise just comment it out).
lda #$35 ;Kernal off to allow
sta $01 ;usage of Hi-Mem.
ldx #$00 invchr
lda $f400,x ;Status charset
eor #$ff ;Reverse bits
sta $f400,x ;Store back again
lda $f500,x ;Status charset 2
eor #$ff ;Reverse bits
sta $f500,x ;Store back again
bne invchr ;Do 256 times until
jmp $4245 ;Jump to SEUCK game
initializing of the front end is ;complete,
so now we work on the main ;front
end source. This will be placed ;in
a new position.
*= $6580 frontend
sei ;Set interrupt flag
want to switch off all interrupts ;that
were used in the game.
lda #$0b ;Screen off
lda #$00 ;No sprites
sta $d020 ;Border+BGR Colour
sta $01 ;Restore kernal
the bitmap picture colour data ;and
put it into the main front end's ;position.
We do this by reading 9 rows ;and
drawing each row by 40 columns.
ldx #$00 ;Set loop to 0 setcols
lda $8400,x ;Row 1 data
sta $d800,x ;Row 1 store
lda $8428,x ;Row 2 data
sta $d828,x ;Row 2 store
lda $8450,x ;Row 3 data
sta $d850,x ;Row 3 store
lda $8478,x ;Row 4 data
sta $d878,x ;Row 4 store
lda $84a0,x ;Row 5 data
sta $d8a0,x ;Row 6 store
lda $84c8,x ;Row 7 data
sta $d8c8,x ;Row 7 store
lda $84f0,x ;Row 8 data
sta $d8f0,x ;Row 8 store
lda $8518,x ;Row 9 data
sta $d918,x ;Row 9 store
cpx #$28 ;(#40 chars???)
bne setcols ;draw next column
the front end colour data (as for ;this
simple tutorial, only one screen ;is
used for text. The text is also ;stored
to the screen area which we use. ;Text
colour data will be drawn from the ;10th
ldx #$00 ;Set loop X to 0 drawcls2
lda $8140,x ;Read colour data
sta $d940,x ;Store per char
lda $8200,x ;Read colour data
sta $da00,x ;Store per char
lda $82e8,x ;Read colour data
sta $dae8,x ;Store per char
inx ;Add 1 to loop
bne drawcls2;Do max 256 chars
part is the main fun part. We are ;going
to add some interrupts and raster ;splits
to the code, but before we can ;do
this. They need to be initialised.
lda #<irq1 ;Store low/hi bytes
ldx #>irq1 ;of interrupts to
sta $0314 ;the IRQ register
stx $0315 ;flag.
lda #$7f ;Enable CIA to sync
sta $dc0d ;with interrupts
lda #$2e ;Initialised raster
sta $d012 ;position.
lda #$1b ;Screen on
sta $d011 ;
lda #$01 ;Sync IRQ vectors
lda #$00 ;Song number
jsr $9000 ;Initialise music at
lda #<message ;Initialise
sta messread+1 ;scroll text
message for the scroll text. We ;will
use the .txt prompt to write a ;scroll
text - although there are other ;possible
.text " ... welcome to - gr"
.text "ayhawk - ... game de"
.text "sign, graphics and sou"
.text "nd effects were done b"
.text "y alf yngve using the "
.text "shoot 'em up construct"
.text "ion kit by sensible so"
.text "ftware ... front end"
.text " programming was done "
.text "by richard bayliss ..."
.text " bitmap logo was dra"
.text "wn by johan janssen .."
.text ". music was composed"
.text " by richard bayliss .."
.text ". copyright (c)2014 "
.text "the new dimension ... "
.text " mission briefing: i"
.text "t has come to attentio"
.text "n that deep in space, "
.text "an alien threat awaken"
.text "s ... aliens are sto"
.text "ring substances on hug"
.text "e asteroids ... thes"
.text "e could result to deva"
.text "stating consequencse, "
.text "should they be used to"
.text " build deadly weapons "
.text "... you must pilot a"
.text " greyhawk fighter ship"
.text " across all of the ast"
.text "eroids, and destroy ea"
.text "ch one (after you have"
.text " passed over it) ... "
.text " the asteroids are hea"
.text "vily guarded by the al"
.text "iens, which you must a"
.text "lso blast ... can yo"
.text "u destroy all of the a"
.text "steroids and whatever "
.text "is left on them, or wi"
.text "ll the galaxy be doome"
.text "d forever? ... there"
.text " is only one way to fi"
.text "nd out ... press fir"
.text "e to start the game .."
Superb, the listing is typed in. However, save the code using BACK
ARROW+W (Unless you are just using the .D64 you downloaded to try it
out) and then press BACK ARROW+3. If it doesn't work the first time and
the routine jumps back to the assembler, add the following in at the
very top of the source code:
Note ... If you want to load the example game and the listing that is
already on the tutorial example disk, you must load in the RAW SEUCK
game file (Which was saved using the SAVE AS FINISHED GAME option). Do
the 3 steps before (The F 6580 B6C0, tips, etc). Press the RESET button
and select the fastload option. Load in the TITLEDATA then enter the
turbo assembler. Load the sequential version of the listing using BACK
ARROW + E and type in FRONTEND.SRC*.
The listing will then load in. Now type the 2 lines (indicated in
yellow above the previous paragraph). Assemble and run. A READY. prompt
SAVING / TESTING YOUR FINAL PIECE
We are nearly there now.
It is time to save the game, and to do that you will need to go into
the Machine Code monitor in Fastload (Or freeze mode). Save the
filename as follows:
This will save the whole game to disk from $0810 (Where we added the
SEUCK title skip init routine) all the way to $FFFA. The file size will
be 249 blocks. Type in G 0810 to run the game. Voila. A new front end
linked to your SEUCK game.
Is this the end of it? Not quite. It is time to make the file size
shorter. What do we do? ... Crunch it.
There are two different ways how you can crunch the finalized game.
There is use of a packer and a cruncher (On the disk is Zipper V5.0 and
2MHz Time Cruncher V5.0 for fast speed).. Or you could just extract the
finished production with a .D64 editor and compress it all with
PuCrunch or Exomizer. Here's the oldschool method ...
- Load in Zipper V5.0
- Enter the load name of your SEUCK game with the new front end
- Enter the save name of your SEUCK game with the new front end
- Enter $0810 as the jump address - since that is where the init front
end skip routine lies
- Enter $37 as the $01 value
- Enter SEI in the SEI / CLI option
- Wait for the file load and pack.
- When the border is grey (with nothing happening), press SPACEBAR to
save your packed game
If you load in the compressed game game (before using a cruncher)
you'll need to type in SYS2049 to run it to see if it works. If it
does, then the next stage just for you.
- Load in 2MHz Time Cruncher V5.0
- Enter the load name of the game, which you compressed using Zipper
- Enter the save name of the crunched game
- Enter $0801 (not $0810) as the jump address - since that is where the
decruncher from Zipper V5.0 commences
- Enter $37 as $01 Value
- Crunching step = speed (1 is fastest crunch speed), the higher the
step, the better result, but slower ther crunch gets).
- Start loading and crunching the file, by pressing the Spacebar
- Wait a few minutes during crunching
- Select Save option
- Select RUN program option. The screen should blank and then come on
and execute the Zipper decruncher which will then run the game.
That's it, job is done.
THE PUCRUNCH EXOMIZER METHOD
If the packing/crunching method takes too long for you, then we
recommend usage of PuCruncher or Exomizer. Exomizer gives out the best
results, but the decruncher takes longer, where is PuCrunch crunches as
hard as possible and gives a shorter decrunch.
- Use a PC D64 editor to export your PRG of the game
- Use the command prompt to call the directory where PuCrunch is
- Enter as follows: