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Old enough to have known the golden age of Amstrad and Amiga ;)
Still own a few Tilt and Joystick magazine (yeah, I am french).
Professional software architect, hobbyist gamedev.

Game & experiments repo: https://github.com/freds72

Twitter account: https://twitter.com/FSouchu

Thick line drawing routine (as a reply to @JadeLombax Twitter).

Cart #rabogemeri-0 | 2020-07-29 | Code ▽ | Embed ▽ | No License


linefill x0 y0 x1 y1 r [col]
draw a 2*r pixel wide line
note: r must be >= 0.5 to produce meaningful results
note: the code uses sub-pixel precision rasterization, allowing smooth movement


-- 4 pixel wide white line
P#80095 2020-07-29 16:32 ( Edited 2020-07-29 16:35)

introduced in 0.2.0d
how to reproduce:

  • call tline with a start point outside of screen boundaries
  • tline starts at 0 without adjusting lookup coordinates

repro cart:

Cart #kuwirapima-0 | 2020-04-24 | Code ▽ | Embed ▽ | No License

P#75284 2020-04-24 12:30 ( Edited 2020-04-24 12:33)

How to reproduce:

  • switch to spritesheet
  • select pen tool
  • draw
  • middle-mouse click to pan
  • draw does nothing outside the initial zone
P#74884 2020-04-17 15:52

How to reproduce:

-- outputs zero
local b=band(nil,4)
-- throws error (arithmetic on field ?)
local b=nil<<4
P#74869 2020-04-17 07:07

How to reproduce:

  • cart with 3 includes
#include includes/bold.lua
#include includes/bigscore.lua
some other code
#include includes/tquad.lua
  • reports invalid 'printb' not found (included in bold.lua)
  • info produces random output:
  • ctrl-r clears the error and runs the cart ok
P#74868 2020-04-17 07:00 ( Edited 2020-04-17 07:01)

how to reproduce:

for i=1,n do



Repro cart:

Cart #towakowibo-0 | 2020-04-17 | Code ▽ | Embed ▽ | No License

P#74867 2020-04-17 06:36

Multicart is really a nice expansion feature, to offer content beyond the 32K boundary.
However, with reload not supporting BBS-hosted carts, large games are banned from BBS.

Is that something considered in the pico roadmap to bring back multicart games to the "official" forums?

Note that supporting more than a couple of data carts will require rework of the BBS file management.

  • support for upload many files at once
  • support for listing cart identifiers
  • support for headless export of p8.png (limited to html/bin at time of writing)
  • ability to assign same id pattern to many carts (ex: vracing_0... vracing_10)


P#73670 2020-03-04 19:53

As per documentation, reload does not support BBS carts.
However, the function fails without any error while trying:

-- does nothing (or not??)

Could the function reports an error in such case?

P#73597 2020-03-01 21:42 ( Edited 2020-03-04 19:54)

On Chrome: Version 79.0.3945.88 (64 bits)
How to reproduce:

  • navigate to any game
  • click on "code" dropdown
  • page becomes unresponsive (cannot be selected, game cannot be launched...)

Not reproduced on Edge (and apparently on Firefox - cannot test)

P#71715 2020-01-02 21:05 ( Edited 2020-01-02 21:48)

Cart #freds72_snow-3 | 2019-12-08 | Code ▽ | Embed ▽ | License: CC4-BY-NC-SA

Winter is coming (as every year actually...), time for some skiing!
Enjoy going down the slope, trying to beat your previous track record or freeriding skills!

Grab coins for some extra time bonus - watch out for off track hazards!
Your polar jacket can sustain a couple of direct hits, avoid trees anyway...

Note: there is no end racing line - you will loose :] question is how much time will you last?


  • Left/Right: control direction
  • c: jump (hold to charge)
  • x: restart (if stuck)
  • follow GPS pointer if lost


  • blue: easy
  • red: moderate, with side tracks. Practice your tricks.
  • black: heavy slope, with side tracks. Tricks or time out :)

About the PICO-8 Advent Calendar

This winter another group of PICO-8 elves has worked hard to release a shiny new toy every day in December. Check out the Pico-8 Advent Calendar 2019 each day for a new surprise!

There's even more festive fun waiting on last year's calendar! https://www.lexaloffle.com/bbs/?tid=32388

Happy Holidays!


Before I joined the ranks of the Advent Calendar 2019, @johanp, @p01 and others were toying with terrain generation - resulting in this:

With the theme being set to winter, I had this prototype ready to test the idea:

The gameplay evolved from some endless runner to something more akin a time attack game.
Thanks to feedback from early testers, and several gameplay changes, I think I have something that is fun to play and challenging enough!

Source code (+unminified version): https://github.com/freds72/midwinter

Update 1.3

  • updated: high level gameplay :]
  • know bug: minor visual artifacts on black track (due to the way I cull terrain)


  • Advent Calendar folks! ( @enargy :)
  • Midwinter mask: Andrew Elkerton (I guess...)
  • intro music: @gruber_music
  • trifill: @p01
P#70497 2019-12-02 19:39 ( Edited 2019-12-08 18:18)

Cart #ellipsefill-0 | 2019-08-20 | Code ▽ | Embed ▽ | License: CC4-BY-NC-SA

A little experiment with filled ellipse, supporting any rotation angle (the tricky part!).
The code is moderately fast as it finds the root of the ellipse equation to get the segment extent for each row.

Car headlight example use:

P#66809 2019-08-20 20:47

A couple of devs are investing into multicart games (like 5 or more data carts).
We are all put back by the artificial loading times (eg minutes)

Would it be possible for the fat client to either ignore load time throttling, or only activat throttling for the published version?
I want the multicart multiverse, not loading screens ;)

P#66040 2019-07-23 06:44 ( Edited 2019-07-23 06:46)

Using the cough undocumented cough stat(102) from a game hosted on itch.io, I got back:


This is indeed the url of the iframe (which doesn't help).
A more correct behavior would be to report the parent page url, with the benefits of:

  • having a predictable outcome
  • actually preventing rogue hosting (somehow...)

Note: Looking at the HTML, I see that url is retrieved from:

var str = window.location.hostname;

Using that alternate code would fix the bug:

var str = (parent !== window) ? document.referrer : document.location;
P#65996 2019-07-21 08:37

Ce post est la version française de: PICO-8 Giveaway

Initié par @Liquidream, plusieurs developpeurs offrent des licences pico8 à des jeunes (et moins jeunes) qui n'auraient pas les moyens mais pleins d'idées!


Pour avoir une chance de gagner, repondez à la discussion officielle avec un petit message:

  • pourquoi vous voulez une licence?
  • quel jeu(x) comptez-vous créer?

Les Règles

  • Ouvert à tous (sauf ceux qui peuvent se payer une licence ET un sandwich!)
  • Une seule entrée par personne
  • Date de cloture (ouch!) Samedi 6 Juillet @ 11:00 (heure Paris)
  • Les gagnants seront choisis au hasard
  • Il y aura autant de gagnants que de licences offertes
  • La licence sera attribuées via un compte mail (message privé)

Bonne chance 😁🤞

P#65558 2019-07-04 19:16 ( Edited 2019-07-05 06:12)

Ghost Rally

Cart #grally-0 | 2019-06-02 | Code ▽ | Embed ▽ | License: CC4-BY-NC-SA


The game is a race-against-yourself rally game. It features accurate rigid body physics and car handling.
Goal is to beat yourself every lap!

Enjoy racing as in the 80's, whith over powered cars very close to the public!
tip hitting any of the lil' dudes:
incurs a +5s time penalty :]

warning the game is complete yet the car handling is really picky - I am releasing it as is, as I can't tweak the gameplay without breaking the physic engine :/


  • left/right: turn
  • up/down: accelerate/brake
  • c: recover (when flipping over!)

Dev Log

Source code & tools: ghost-rally


Sound effect code: taken from @tiagosr rally game
Trifill: @p01

Physic Engine

Physic engine was started from scratch following Barraf's 'classic' paper.
I quickly dropped this version as it relied too much on numeric convergence !

The current version uses part of Randy Gaul C++ physic library and underlying principles.
The key aspect to get stable collision is to resolve impacts only for the incident face, e.g. the plane most facing the ground:

This is obviously an heavily simplified version, limited to dynamic-to-static resolution.
Randy's engine architecture relies on very few magic constants and is extremely stable (well, as long as pico numbers don't get in the way!!).

The physic engine is designed as an extension a generic 3d actor class and can easily be taken out for other games.

Car Physic

The car is modeled using a front and rear tire. Each tire has lateral and longitudinal forces, as detailed in this article: The Racing Line - Combined Tyre Forces.
Other good readings:
Car Physics for Games
Box2d Top Down Racing Game

The gif above shows forces applied to the car and their application point:

  • G force (down)
  • read tyre pushing car (with a lateral component to counter slide)
  • front tyre and turning forces (again with a lateral component)

Slip angle and slip ratio curves are defined using SFX 4 and 5 - tweak them to see effect in game!


The game started as a terrain renderer using marching squares.
Terrain height map is 64x64, displayed as a 128x128 grid to display marching square "diamond tiles":

Textured Car

The car is textured mapped, using a custom version of @p01 trifill.
The Blender model directly references an export of the cart spritesheet.


The game uses my usual Blender/Python export toolchain.
A custom terrain editor is available as a pico-8 cart (contact me if needed)

P#64950 2019-06-02 14:33 ( Edited 2019-06-04 20:11)

I am writing data to a p8 file from a Python program - format for 0x0-0x3200 ROM range is ok.
Issue is sfx section - each sfx (68 bytes) is actually written as 84 bytes (??) with empty bits left and right.
I have no clue what is the masking/bitshifting/... logic between my input value and the resulting p8 string.






P#64268 2019-05-09 18:44 ( Edited 2019-05-09 18:49)

Case solved: issue was triggered by one of my USB sticks constantly sending inputs

When exporting Tiny Sim, some keys are stuck:

P#64164 2019-05-03 14:25 ( Edited 2019-05-04 09:17)

Cart #numakunawa-0 | 2019-04-08 | Code ▽ | Embed ▽ | No License

FPS demo cart as an answer to @MBoffin April 1st Twitter joke.
Stay tuned for technical details.

P#63343 2019-04-08 21:27

Cart #doyusuyepo-0 | 2019-05-04 | Code ▽ | Embed ▽ | No License

Project started following a question on 3d clipping on this forum and quickly spiraled into a full blown 3d renderer with support for real-time shadows and camera space clipping :/

Shadows are calculated in real-time by extruding a shadow volume from each lit face.
Resulting polygons are added to the face and rendered/sorted with the face.

The shadows are globals e.g. self-shadowing is supported, see torus scene.

Performance-wise this is bordering what pico can support, as many clipping operations are required to generate shadow polygons. There is room for optimization (vertex cache, smart selection of clipping planes) left to the reader!


Project (including how to add custom 3d models) is available here: github


  • 3d papers from the 70s/80s are pure gold!
  • trifill function from @p01

Update 1.1

  • fixed polygon gaps (using correct middle screen position + ceil)
P#60772 2019-01-12 14:38 ( Edited 2019-05-04 12:54)

How to reproduce:

  • go to a game page
  • launch game
  • go to comment section
  • type some text

Bug: nothing appears (input is captured by pico)

Workaround: refresh the page / don't launch game before posting comments.

P#59908 2018-12-11 21:38 ( Edited 2018-12-11 21:38)

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