GPI [Lexaloffle Blog Feed]

Crash with metatable

Thu, 05 Jun 2025 16:27:30 UTC

copy and paste this code (with "puny font"-mode - ctrl+p)

cls()

storage_readfn={peek,peek2,nil,peek4,[0]=bitread}
storage_writefn={poke,poke2,nil,poke4,[0]=bitwrite}

storage_adr=0x8000

storage_metabytefield={
 __index=function(t,key)
  return t.read(t.adr+t.byte*key)
 end,
 __newindex=function(t,key,value)
  t.write(t.adr+t.byte*key,value)
 end,
 __len=function(t)
  return t.len
 end
}

storage_metadata={

 __index=function (t,key)
  local m=rawget(t,"_storage")
  if tonum(key) then
   local adr,byte,size=unpack(m._num)
   if (key>0 and key<=size) return storage_readfn[byte](adr+byte*key)
  elseif m[key] then
   local adr,byte=unpack(m[key])
   return storage_readfn[byte](adr)   
  end
 end,

 __newindex=function (t,key,value)
  local m=rawget(t,"_storage")
  if m._num and tonum(key) then
   local adr,byte,size=unpack(m._num)
   if (key>0 and key<=size) storage_writefn[byte](adr+byte*key,value)
  elseif m[key] then
   local adr,byte=unpack(m[key])
   storage_writefn[byte](adr,value) 
  else 
   rawset(t,key,value)
  end
 end,

 __len=function(t)
  local m=rawget(t,"_storage")
  return m._num and m._num[3] or 0
 end,

 __pairs=function(t)
  local stage,v=1
  return function(t,k)
   --numbers
   if stage==1 then
    k+=1
    if t._storage._num and k<=#t then
     v=t[k]
    else
     stage,k=2
    end
   end   
   --storage
   if stage==2 then
    repeat    
     k,v=next(t._storage,k)
    until k!="_num"
   if (k) v=t[k] else stage=3
   end
   --normal table
   if stage==3 then
    repeat
     k,v=next(t,k)
    until k!="_storage"
   end
   return k,v
  end,t,0
 end

}

function storage_reserve(list,table)
 local oldtable={}
 table=table or {}

 table._storage=table._storage or {}
 setmetatable(table,storage_metadata)

 local byte=1
 for txt in all(split(list,"\n")) do
  if (sub(txt,#txt)=="]") txt=sub(txt,1,#txt-1)
  local c=ord(txt)
  if txt=="" or c==45 then
   --commend
  elseif c==91 then
   --[
   local size=tonum(sub(txt,2))
   table._storage._num={storage_adr-byte,byte,size}
   storage_adr+=byte*size
  elseif c==42 then 
   --*
   byte=tonum(sub(txt,2)) 
  elseif c==62 then
   -->
   txt=sub(txt,2)
   add(oldtable,table)
   local ntable=setmetatable({_storage={}},storage_metadata)
   rawset(table,tonum(txt) or txt,ntable)
   table=ntable
  elseif c==60 then
   --<
   table=deli(oldtable)   
  else
   table._storage[txt]={storage_adr,byte}
   storage_adr+=byte
  end   
 end
 return table
end

storage_reserve( [[
>x
*1
hallo
>welt
[3]
<
-- txt
*2
score
xyz
>player
x
y
<
<
*1
>data
>1
[3]
<
>2
[3]
<
>3
[3]
<
<
]],_ENV)

x.hallo=10
x.score=512
x.xyz=0x7fff
x.neu="abc"
x.welt[1]=15
x.welt[2]=27
x.welt[3]=33
x.welt[4]=99
x.player.x=1003
x.player.y=1004
for k,v in pairs(x) do
 ?"entry:"..k.." = "..tostr(v)
 if type(v)=="table" then
  for k2,v2 in pairs(v) do
   ?"entry:"..k.."."..k2.." = "..tostr(v2)
  end
 end
end
for v in all(x) do
 ?v
end

for x=1,3 do
  for y=1,3 do
  data[x][y]=y*10+x
  end
end
?data[1]
stop()

run the code
it should output some code, now type:

?data[1]

pico-8 will close without error message.

procgen universe example

Sun, 30 Mar 2025 08:12:38 UTC

procgen universe example

by GPI

[Click to Play]

Based on this video:
https://www.youtube.com/watch?v=ZZY9YE7rZJw

Generates a procedural universe - with many suns, planets and moons.

And additional to the video, name suns and populated planets.

I used the rnd and srand-function from pico8 instead of the own function.

You can move with the cursor-keys and click on the suns for more details.

Name Generator

Sat, 29 Mar 2025 16:00:54 UTC

namegenerator

by GPI

[Click to Play]

A simple name generator that should generate reasonably pronounceable names.

From a list of approximately 9,000 first names, I created a 26 x 26 table. This table contains the number of times a letter follows another letter.

The name is then generated by selecting a letter and determining the next letter based on its probability.

edit: stupid mistake in the data-creation - update. Should now generate better names. Also enforce that a vocal is on the first or second place.

Rockfall

Sun, 23 Mar 2025 15:37:27 UTC

gpi_rockfall

by GPI

[Click to Play]

Sourcecode + Stand-alone-versions:
https://github.com/GPIforGit/rockfall/releases/

Rockfall is my interpretation of Boulder Dash from 1984. You play Rockford, who tunnels through dirt to collect gems. Gems and rocks are fixed until the dirt under them is removed, then they fall and become a hazard.
Your goal is to collect as many gems as possible and leave the cave through the exit. The exit only opens once you've collected enough gems. After completing a cave you get points depending on how many gems you collected and how much time is left. Every 500 points you get an extra life.
Every five caves, you have a chance to earn an extra life in the intermissions. If you fail, you don't lose a life.

Control:

Title-Screen

X = Start a game
O = Show the solution of the selected cave

Game

direction - move rockford
X - Grow/collect without moving
O - Look around

Elements

Caves

All caves are new or reinterpretations from Boulder Dash. Those who prefer the original caves should look further down.
Don't forget: You can display a solution by pressing O on the title screen.

Level Editor

There is also a level editor:
https://github.com/GPIforGit/rockfall
You need the rockfall-game.p8 and the rockfall-editor.p8 - don't rename them! Copy both to a new directory.
First you should edit the edition and author variables in rockfall-game. Don't use spaces in the edition-variable. Before you export the game, you should run it ones - it will automatically import all levels from the level-editor.

Boulder Dash I + II

And as a bonus: all levels from Boulder Dash I+II as "classic-edition":

gpi_rockfall_classic

by GPI

[Click to Play]

Additional Information:

https://www.boulder-dash.nl/
https://codeincomplete.com/articles/javascript-boulderdash/
https://web.archive.org/web/20231129174205if_/http://www.bd-fans.com/Files/FanStuff/Programming/decodecaves.c
https://boulder-dash.com/

Jumpguy - jump'n'run tech demo

Fri, 13 Oct 2023 07:05:15 UTC

jumpguy

by GPI

[Click to Play]

I work at the moment on a jump'n'run-Game. One of my goals are to have a better camera-control than simple center the player in the middle, the camera should "look ahead".

Don't expect any game here, it is more a "prove of concept"-demo.

Control:
X for jump
o for grabing things

down+jump - fall down on "half-tiles"
stand+up - look up
stand+down - look down.

there is a coyote-time, that you can jump for a short time, when you run over a "cliff".
up - run on "half-tiles-slopes" (the green on the right side, behind the "secret"-Wall

memset(0x8000,0,0x8000)

Sun, 01 Oct 2023 15:57:38 UTC

it is not possible to delete the high-memory with one memset-command

 poke(0x8000,1)
 poke(0xffff,1)
 ?peek(0x8000)--1
 ?peek(0xffff)--1
 memset(0x8000,2,0x8000)
 ?peek(0x8000)-- still 1 / should 2
 ?peek(0xffff)-- still 1 / should 2
 memset(0x8000,2,0x7fff) -- 
 ?peek(0x8000)--2
 ?peek(0xffff)--1

the first memset is ignored, because 0x8000 is -1

Puzzle Duck

Wed, 27 Sep 2023 10:20:53 UTC

Puzzle Duck

puzzle_duck

by GPI

[Click to Play]

A simple Puzzle Bobble / Bust-a-Move - Clone.

from URL Wikipedia:
Puzzle Bobble,[b] internationally known as Bust-A-Move, is a 1994 tile-matching puzzle arcade game developed and published by Taito.

At the start of each round, the rectangular playing arena contains a prearranged pattern of colored "bubbles". At the bottom of the screen, the player controls a device called a "pointer", which aims and fires bubbles up the screen. The color of bubbles fired is randomly generated and chosen from the colors of bubbles still left on the screen.

The objective of the game is to clear all the bubbles from the arena without any bubble crossing the bottom line. Bubbles will fire automatically if the player remains idle. After clearing the arena, the next round begins with a new pattern of bubbles to clear. [...] The fired bubbles travel in straight lines (possibly bouncing off the sidewalls of the arena), stopping when they touch other bubbles or reach the top of the arena. If a bubble touches identically-colored bubbles, forming a group of three or more, those bubbles—as well as any bubbles hanging from them—are removed from the field of play, and points are awarded. After every few shots, the "ceiling" of the playing arena drops downwards slightly, along with all the bubbles stuck to it. The number of shots between each drop of the ceiling is influenced by the number of bubble colors remaining. [...] If they cross the line at the bottom then the game is over.

Special bubbles

Fire

	[8x8]

When you shoot on a fire bubble, it exploded.

Water

	[8x8]

When a bubble hit the water bubble, all bubble below it will be recoloured to the colour of the hitting bubble.

Flash

	[8x8]

Destroy all bubbles left or right from hit.

Joker

	[8x8]

Remove all bubbles with the same colour of the hitting bubble.

Game modes

Puzzle

Single player game, simple clear all 99 levels.

VS CPU

Play against a cpu all 99 levels. At the beginning the cpu is very slow and stupid, but will increase in the higher levels.
You can send bubbles to the cpu field, when you drop bubbles from your field.

VS Human

Two player game. Every player has three lives. When you win a round, you steal a live from your opponent.

Editor

There is an inbuilt level editor, to run it, load the cartridge and type

run "edit"

With left/right choose your level, left click will place a bubble, right click will remove it. To store the level, hit the S-Key or click on the save button. Don't forget to save the Cartridge (ctrl+s) otherwise your work will lost.

Feel free to publish your own level pack!

Download

Download for native windows, mac, linux and raspi version can be found here: https://gpi.itch.io/puzzle-duck

Music

Puzzle Bobble Main Theme
Composition by ‎Kazuko Umino and Yasuko Yamada

Pico-8-Version based on the version from Thomas Alberg
https://musescore.com/user/17124701/scores/3979026

[manual]for TBL[FN()]+=1, FN() will be called twice

Wed, 27 Sep 2023 09:42:50 UTC

according to the manual:

 A += 2   -- EQUIVALENT TO: A = A + 2

// note that the LHS appears twice, so for TBL[FN()]+=1, FN() will be called twice.

ok, let's test it:

 function fn()
   print("in function")
   return 1
 end

 f={ 10 }
 print("f[1] is "..f[1]) 
 f[fn()]+=1
 print("f[1] is "..f[1])

the function fn is only called once!

Mosaik

Sun, 13 Nov 2022 13:24:29 UTC

mosaik

by GPI

[Click to Play]

Crillion

Sun, 30 Oct 2022 13:23:22 UTC

crillion

by GPI

[Click to Play]

A very simple game. Your goal is to destroy all blocks. The problem: You can only move the ball horizontally, the ball moves up and down automatically.

Crillion is an adaptation of the game of the same name on the C64. This release contains the levels of the three official Crillion releases: Crillion, Crillion '93 (hard), Crillion II (very hard). In addition, the levels of Brainion are included, which are designed more than puzzles. And "Junior" from Crillion Junior - a very easy level set.

Rules

Block

	[64x8]

In order for the blocks to break, the ball must be the same color as the blocks.

Changer

	[64x8]

This allows the ball to be colored.

Skulls

	[8x8]

Skulls destroy the character.

Rings

	[64x8]

Rings can be pushed in one direction if the color matches the ball.

Download

Binaries for Linux, MacOs, Raspi and Windows:
https://github.com/GPIforGit/crillion/releases

Episodes

This release contains the levels from

Crillion

Published in Happy Computer, 1988/07
https://archive.org/details/happycomputer-magazine-1988-07/page/n51/mode/2up
By Oliver Kirwa
https://www.c64-wiki.com/wiki/Crillion

Crillion '93

Published in 64'er Sonderheft 85
https://archive.org/details/64er_sonderheft_85/page/n5/mode/2up
http://www.homecomputerworld.com/64ersh.html
By Oliver Kirwa
https://www.c64-wiki.com/wiki/Crillion_%2793

Crillion II

Published in 64'er Sonderheft 54
https://archive.org/details/64er_sonderheft_54/page/n7/mode/2up
By Oliver Kirwa

Brainion

Published in "Digital Talk #104"
https://digital-talk.github.io/
By "The Joker" and "Dr.Guru"
https://www.c64-wiki.de/wiki/Brainion

Crillion Junior

https://www.c64games.de/phpseiten/spieledetail.php?filnummer=7614
by holy moses

Level editor

A level editor is available. It is based on "jaP8e" ( https://www.lexaloffle.com/bbs/?tid=49307 ) and must be copied to the "libs" directory of "jaP8e".
https://github.com/GPIforGit/crillion/blob/main/moduleCrillion.lua

Credits:

Oliver Kirwa for Crillion, Crillion'93, Crillion-Construction-Kit and Crillion II.

"The Joker" and "Dr.Guru" for Brainion

holy moses for "Crillion Junior"

Darrell Flood for the "Sloppy Paint" font (used for the Logo)
https://www.dafont.com/de/sloppy-paint.font

Request - Developer Mode

Sat, 01 Oct 2022 19:34:32 UTC

SDK-Units of consoles have normally more memory.

This can be useful during developing - simple try something without care about limits. Or store additional debug information.

it would be nice, if pico-8 would emulate this.

This can be done very simple:
The project must be saved as ".p8"-utf8-file.
When the project hit the limit of characters, compressed size and token it will display the known warning with a little addition: "Ignore? (Project can't be exported!) (y/n):" - when you hit y - it will start anyway. Save as .p8 is always possible, since there are no limits.
Of course the export to bin, web, rom, png or whatever is not possible. also the cli-command "-run" should not work on this oversized p8.

This would be usfull, when you want to check, if something work. Or when you developed a tool / level editor for a game, which you don't want to share.

additional it would be nice to have an debug - enddebug - command

function test(a,b)
 debug 
   if not a or not b then
     print("this should not happen! Got nils!")
   end
 enddebug
 ...
end

this code should only start when pico-8 is in devoloping-mode.
when it saved to p8.png ( or p8.rom, bin, web), pico-8 should interpret this as comment.

function test(a,b)
 --[[ 
   if not a or not b then
     print("this should not happen! Got nils!")
   end
 --]]
 ...
end

So the token-limit should not be affect by the debug - enddebug block.

Custom font with variable width and latin letters

Wed, 28 Sep 2022 18:08:46 UTC

variablefont

by GPI

[Click to Play]

A very simple font. A little bit bigger than the original, but better readable.
the UTF Latin-1-Suppliment-Characters are included instead the Japanese characters.

type

load "#variablefont"

in pico-8 to load the cartridge.

Created with jaP8e - https://www.lexaloffle.com/bbs/?tid=49307

[bug] compression error

Mon, 12 Sep 2022 20:31:32 UTC

I tried to decompress the source code of my dithering-demo:
https://www.lexaloffle.com/bbs/?tid=49309
and my code failed.

First i thought my code is wrong, I translated from this source:
https://github.com/dansanderson/lexaloffle/blob/main/pxa_compress_snippets.c
the decompress-code to lua, so it is possible that I made a mistake.

I can't find a erro, so I looked at the rom-data:

4300  00 70 78 61 03 BC 02 39 02 40 C1 AC CE 6D 8C 2E  .pxa.¼.9.@Á¬ÎmŒ.

the first 8 bytes (00 70 78 61 03 BC 02 39) are the header, so the first databyte is 02
or binary: 00000010

When I look in decompress code:

while (src_pos < comp_len && dest_pos < raw_len && dest_pos < max_len)
	{
		int block_type = getbit();

		// printf("%d %d\n", src_pos, block_type); fflush(stdout);

		if (block_type == 0)
		{
			// block

			int block_offset = getnum() + 1;
			int block_len = getchain(BLOCK_LEN_CHAIN_BITS, 100000) + PXA_MIN_BLOCK_LEN;

			// copy // don't just memcpy because might be copying self for repeating pattern
			while (block_len > 0){
				out_p[dest_pos] = out_p[dest_pos - block_offset];
				dest_pos++;
				block_len--;
			}

it read the first bit (a zero) from 0x02 and go through the block_type==0 code.
At this moment the out_p is complete empty and dest_pos is 0, so when the code comes to "out_p[dest_pos] = out_p[dest_pos - block_offset];" it copied data BELOW the output-buffer.

Dithering demo

Mon, 12 Sep 2022 16:50:04 UTC

yemapepoke

by GPI

[Click to Play]

A little demo of importing dithered pictures. The rom contain 3 pictures, switch with x/o.

Images are created with jaP8e
https://www.lexaloffle.com/bbs/?tid=49307

jaP8e - Editor for code, graphic, charset, sound

Mon, 12 Sep 2022 15:56:08 UTC

Features

Source code in lua!
Editor for sprite, map, sound, music, charset
Map editor with support of custom width / size
Name sound and music
Custom palette with the extended 128+ color-ids (32 Colors in total)
Charset editor with possible to export single characters and variable width
Hex editor to copy & past memory to pico-8 string (URL raw memory access format )
Modular design
Import images as sprite sheet, map(!), label - with optional dithering

IMPORTANT

This is a beta release! This means, there are bugs, the program can crash. Make backups before using the editor.

Download

https://github.com/GPIforGit/jaP8e/releases

basic control/setup

Set the path to pico-8.exe

jaP8e needs to know where the pico-8 execute is. Choose in the Menu the "Pico-8" > "Set Pico8 exectuable" option to set the path. Otherwise it can't run any code or playback sound.

Pico-8 Remote

Since I don't know how to program sounds like in pico-8, jaP8e can't playback sound by default. But it is possible to start a "Remote"-pico-8, which runs in the background and is controlled by jaP8e. Activate this option in the "Pico-8"-menu. After this you can playback any sound effect and music during jaP8e.
This function starts a pico-8 with the remote.p8 file in the background. I send commands through stdin/stdout to this remote.

Change Values in the grey input boxes

You can change the values of the grey input boxes by left click in it and use the keyboard. Alternative you can press and hold the right mousebutton and change the value with x-mouse-movement. The third possibility is to use the mouse wheel over the input fields.

basic layout

On the top you find the modules-tab to switch the editors. On the right top side are currently open files. A Star in the file name indicates that the file has unchanged data.

memory layout

jaP8e "simulate" the memory of pico-8, with a rom and ram section. The rom-section is stored normaly like pico8 does and can access normaly. RAM is stored as meta-data and can't access directly in pico-8, but you can export ram as string to copy in the source code (HEX-Editor).
Also you can reposition the map, sprite, sound, music, spriteflags to any memory location, even when pico 8 doesn't support it.
For example, when you don't use a map in your pico-8-project, you can store there additional sprite data. Simple reposition the sprite to 0x1000 to draw in the map-data. In pico-8 you must manually copy the memory (memcpy) to access this additional sprite data.

Error-message and disable a module

When a error happen, a message box with ok and cancel will open. With ok jaP8e will ignore the error. With cancel the module which cause the error will disabled. At least you can try to save your work when a error happen.

Source Editor

on the left side of the window you find some information tabs:

Functions

display every function that jaP8e found in the current tab. Also all comments which start and end with "--" should be visible here.
You can click in the list to jump to the position.
When the cursor in the source code is inside a function, this function will be highlighted in the list.

Sprites

Fast display of all sprites. When you select a number in the source code, the sprite with the same id is highlighted.
Click on a sprite will add the id-nummer in the source code

Charset

Click on a char to add this in the source code.

Sound

When you select a number in the source code, the sound with the same id is highlighted. Press ALT + SPACE to playback this sfx.

Music

same as sound

Palette

show the custom palette (when not changed, this is identical to default), the default palette and the extended palette

Source code editor

Should react nearly the same as the default editor in Pico-8 with some extras. Tabs work as in Pico 8 - simple click in the "+" above. You can also name the tabs, when the first line is a comment.
When you select a word, it will highlight this word in the complete source code. Also when the cursor is over the a brace the matching other brace is highlighted.
When you don't like the color-scheme, you can edit the jaP8e.ini file.
By default the puny-font is disabled and a normal font is used, so all text should be written in lower case!
Copy & past will always ignore the puny-setting.
Look in the menu for many additional functions / keyboard shortcuts.

Map editor

On the left side you can select a Sprite - you can select more than one.
Grid add a grid, id will display the ids, flags draw a bar with the spriteflags and count shows how often a sprite is used in the map.
With CTRL + Click the current Sprite will exchange the position in the Spritesheet and the map will be corrected.
With CTRL + SHIFT + Click it will exchanged without correction.

You can also quick-select patterns in the map by right click and hold. Middle-Mouse button will scroll and the wheel will change the zoom.

Below you find some options:
Grid will add a grid to the map, ID will draw the ids of the tiles, when find is active, the selected sprites of the sprite sheet will highlighted in the map.
Also you have different tools like stamp, line etc.
With POS you can change the position of the map in the memory and Width will change the width of the map.
With Background you can select a color to change the background.

You can quickselect a sprite with the shift/a/s/d/w-keys

In the Menu with File > import > map image you can import an image as Map! The image will sliced in tiles and added to the sprite sheet, when an empty slot is available.

Sprite editor

Control nearly the same as the map editor.
POS and FLAG-Buttons will change where the sprite / spriteflags are located in the memory.
Set Icon will change the icon when you export an binary.
Right click on the color to change the palette.
Important: Palette changes are stored in the ram-section and must be exported in the hex editor to the source code.

Sound editor

Should work like the original pico-8 editors. Like in sprites you can with CTRL+Click / CTRL+SHIFT+Click exchange the SFX.
You can additonal name a SFX with 8 characters. This information is stored in the meta-data of the p8-file and is only for your information and not directly useable in pico8.

Music editor

Can do the same as the pico8 editor.
When you paste a music, the sfx-pattern will be insert at top by default (pico 8 start at bottom). You can change this behaviour in the edit-menu.

Label editor

Also very basic. You can import an image with the file->import->label image in the menu bar. In the settings-menu you can select activate dithering.

Charset editor

Important note: Charset is always located in the memory section (0x5600). When you want to use it, you must copy it in the hex editor!
Work like the Sprite editor, but only with two colors. On the right button you can set some basic settings. Variable font with is supported, when you activate "Adj.Enable", then you can use the "Adj"-field to change the with of the current char (like in the picture, I is here only 2 pixel with.
When you click on the "lazy dog" text you can switch between different example text.
When you ctrl+c on a char, it will copy as a string, that can be use directly in pico 8 URL pico8-manual. In the edit - menu you can select between binary-char and hexadecimal-char version.
Of course you can paste chars in both formats.

hex editor

On the left side you have some select buttons. The "ROM" button select the default position of the items. Under "RAM" you can select some areas which are used by jaP8e. When you move the Sprite/Map/and so on with the "POS"-button, you can select the area here with the "POS"-mark.
The Hex-Buttons below select the memory 0x8000 - 0xff00 location. Click with shift to select to the end of this memory-block.
You can Copy & Paste memory blocks. It is stored as string in the clipboard in the URL raw memory access format and can be simple copied in the source code!
For example the default palette from memory look like this:

\^@5f100010\0¹²³⁴⁵⁶⁷⁸\t\nᵇᶜ\rᵉᶠ

IMPORTANT all data above 0x4300 are saved as meta-data and are not accessible directly by a pico-8 program.

pico-8-support

In the Pico-8 menu you can start your project. At default jaP8e switch to write protect mode and will reload after pico8 is closed (this can be disabled in the pico-8 menu). Your project must be saved before this will work.
You can also export here binarys (you can select a icon in the sprite editor), webpage, .p8.png and more.
The RAM-Section of the current project will be stored as meta data in the .p8 - file. This is way jaP8e can only p8 files directly.

what is luatik?

Luatik is my lua interpreter variant. I patch lua with some features (auto load libraries, += -= is possible and some other goodies). Look in the lunatik-order to get more information.
https://github.com/GPIforGit/Luatik

[Request] Print (text,"center",y)

Mon, 12 Sep 2022 10:30:05 UTC

I think, that it is common to print a text in center of the screen.

With the variable font it become a little bit complicated..
When the text is variable we must do something like this.

str = "text"
len = print(str,0,-0x4000) -- print outside to get the length
print(str, 64-len\2, 128)

it would be nice, when instead of the x-coordinate a string with the position could be added

str = "text"
print(str, "center", 128)

possible "key-words" would be: "left", "center", "right"
for y would be "top", "center", "bottom"

btw. a "printsize" function would be nice, don't draw anything, only return width and height in pixels.

The Laboratories of Dr. Creep

Sun, 31 Oct 2021 16:09:50 UTC

drcreep

by GPI

[Click to Play]

Recreation of a C64 classic: Castles of Dr. Creep.
Compared to the original there are some changes, on the one hand because the layout is different (40x24 vs 16x16), on the other hand because I have defused some "backtracking" and death traps. Nevertheless, please note, the levels are from 1984 - there you have something different design.

Story

Playing the game

Obstacles

Editor

Working with the editor

behind the scenes

Some may have guessed it already, the game is a "The Castle of Dr. Creep" clone. A classic on the C64 from 1984 and was quite unique at the time.

The original game is relatively complex and uses a complete floppy disk. The problem here is that I wanted to insert as many of the castles as possible. To put them "classically" in the map data does not work, much too large, so a level editor had to be created. Writing it in Pico8 was not so easy, it is almost more complex than the game.

A special feature of the level data is that I do not save byte wise, but bit wise. For example, to save the status of a trapdoor, I need exactly one bit. This method is also used for the game saves, otherwise it would be partly impossible to accommodate this in 256 bytes. However, I had to cheat a bit, for example, a round position of the creatures is stored. It is possible that a loaded game does not always remain solvable. But I think I've solved the problem.

In addition, I use the lzw logarithm to store even more data. it is possible to place data in source code via string, but somehow I find that inelegant. The packed data also has the advantage that it can be edited more easily with tools without changing the lua code.

Compared to the original castle, there are some changes, on the one hand because the layout is different (40x24 vs 16x16), on the other hand because I have defused some "backtracking" and death traps. Nevertheless, please note, the levels are from 1984 - there you have something different design.

The game should be similar to the original, but not just copy it. I've made some changes. The monsters, for example, always go at the closer player (in the original it was always player one). Likewise the map, in the original it appears after each level and you have to confirm it, I immediately switch here to the next room. This increases the game speed enormously.

The story text is a variant of the text on the back of the box. The object descriptions are variants of original tutorial.

sources

LZW-compress and decompress

Sat, 30 Oct 2021 13:10:11 UTC

lzw

by GPI

[Click to Play]

I have translated and extend the lua code from here
https://rosettacode.org/wiki/LZW_compression
I tried to reduce the token count, but I wouldn't surprised when someone will shrink it more.

lzw is the codec that for example gif use, it was patented, but it expired 2004.
more information:
https://en.wikipedia.org/wiki/Lempel%E2%80%93Ziv%E2%80%93Welch

I tested the code with the JELPI-Graphic&Sound data - and it will compress it to 6094 Bytes (from 17152 - ~36%).

With the next update the high-memory above 0x8000 will be useable (at the moment only with a undocumented poke), my plan is to place there 32kbit of graphic and sound data. The problem is, that this memory is not saved and I don't want to store it in the source-code because it is too big.

With this code I can compress the 32kbit and store it in the "rom" (the lower 0x4300 bytes). Create a "build"-cart which fill the 32kbit (for example with the reload()-function from other carts), compress the data and cstore() the compressed data.
Copy the compressed data to the the "game-cart", on start decompress the data in the high-memory-area and copy then the part currently needed in the map/sprite-memory.

About the tape_()-function: Think about it like a "punched tape" - it can be used to store datas with variable bit-size. You can use it also for the "Persistent cart data". Normaly you can place 256 Bytes. When you want for example to save if a door is open or closed, you need only one bit. With this routines you can easily store 256*8 = 2048 Doors. The routine should handle 1 to 16 bit values.

Request - return-value for poke()

Fri, 29 Oct 2021 18:14:03 UTC

it would be nice, when the poke() would return the address after the poke, like print() does.

for example:

adr=poke(adr,1)

should do the same as

poke(adr,1)
adr+=1

adr=poke2(adr,0xffff)

instead of

poke2(adr,0xffff)
adr+=2

str="abcdef"
adr = poke(adr,ord(str,1,#str))

instead

str="abcdef"
poke(adr,ord(str,1,#str))
adr+=#str

Request - Pause-menu position and background

Tue, 26 Oct 2021 18:26:48 UTC

it would be nice to select where the pause menu should appear. Also the possiblity to draw a custom background for the pause.

For example for a RPG. It would be useful to draw the player-status on screen and the pause-menu on the right button of the screen. In combination with the menuitem-command it would be an easy and "cheap" possibility to create a status-menu. Or display a map of the current level, an inventory and so on.

Suggestion:

menustyle([<position>[,<draw-function>]])

position could be 0=top left, 1=top, 2 top right, 3 left, 4 center (default), 5 right, 6 bottom left, 7 bottom, 8 bottem right
And draw-function is a function which is called direct before the pause-menu appears.

GPI [Lexaloffle Blog Feed]

Crash with metatable

procgen universe example

Name Generator

Rockfall

Control:

Title-Screen

Game

Elements

Rockford

Dirt

Rock

Gem

Wall

Metal Wall

Growing Wall

Magic Wall

Exit

Firefly

Butterfly

Amoeba

Slime

Eraser Wall

Caves

Cave A: Intro

Cave B: Labyrinth

Cave C: Loop

Cave D: Pit

Intermission 1: Falling Down

Cave E: Matrix

Cave F: Guards

Cave G: Rooms

Cave H: Puck

Intermission 2: Diagonal

Cave I: Judgment Day

Cave J: Hourglass

Cave K: Butterflies

Cave L: Averlanche

Intermission 3: Circle

Cave M: Snail

Cave N: Timing

Cave O: Demolition

Cave P: Skip It!

Intermission 4: Prision

Level Editor

Boulder Dash I + II

Additional Information:

Jumpguy - jump'n'run tech demo

memset(0x8000,0,0x8000)

Puzzle Duck

Puzzle Duck

Special bubbles

Fire

Water

Flash

Joker

Game modes

Puzzle

VS CPU

VS Human

Editor

Download

Music

[manual]for TBL[FN()]+=1, FN() will be called twice

Mosaik

Crillion

Rules

Block

Changer

Skulls

Rings

Download

Episodes

Crillion

Crillion '93

Crillion II

Brainion

Crillion Junior

Level editor

Credits: