This weekend I was playing around with InterIm to try out some new features (asRefs macro) and some old ones that were not really tested (custom render ops), so I decided to build a drum machine! 🎵

The API could still use some improvements, but this is getting to an almost usable state. 🙂

Font: Spleen by Frederic Cambus ( Drum Samples: Free Pipe Pack by Goldbaby (

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João Costa shared 3 months ago
João Costa shared 4 months ago
João Costa shared 4 months ago

Just released InterIm, an immediate mode GUI library in pure Scala:

Published to JVM/JS/Native and backend agnostic: You give it the current input state and it returns a set of basic operations for you to render.

You can play around with an online example in


Today I was playing a bit with immediate mode GUIs, trying to port the code from

This actually worked pretty well and, while still pretty imperative, I was able to hide some of the ugly mutable code with Scala 3 context functions.

For fun, I also made sure that the code received a structure with inputs and returned a sequence of operations that need to be interpreted. That way it is completely backend agnostic (like microui).

Maybe I'll clean it up a bit (at least to add text support) and open source it. 🙂


OK, I finally took the time to version control all custom changes that I have in this instance:

I needed to do this anyway to comply with AGPL. I'm posting this note just in case someone comes looking for the link - I should probably add the link to the footer, but that's something for the future.

João Costa shared 6 months ago
João Costa shared 6 months ago
João Costa shared 6 months ago
João Costa shared 6 months ago

It's been a while since I entered a gamejam and I won't be able to make it to the next , so I decided to enter MiniJam 130 with another game in .

The themes are "Lunar" and "10 Seconds", so I went for the least original idea: A lunar lander clone with a 10 second time limit.

As usual, you can play it on and check the source code on GitHub.

There are quite a few performance issues (don't try it on Firefox) and I found quite some bugs in Minart during the development. However, it's going to take me a while to fix them, so that will have to wait for a post-jam version.

One of the reasons I like to enter jams once in a while is to find bugs/problems in Minart. On that regard, this was clearly a success.🙂

Debugging some audio problems recently.

How it started:

Fucking Firefox always giving me performance problems, I bet they messed up the WebAudio implementation.😠

How it's going:

How the hell were Chrome, JVM and SDL still playing audio with my stack-exploding accidentally-quadratic code?😬

about the QOA audio format, which seems to be pretty recent - 2 months old, based on the announcement blog post.

It's a simple audio format for lossy audio compression (in the same way that QOI is a simple lossless image format).

This couldn't come in a better time, as I was looking for simple compressed audio formats (and if it's just like QOI, it's going to be great for sure ❤️). Can't wait to take it for a spin.


Just took some time to setup Airflow and convert some old cronjob into a DAG.

This is way overkill for my needs (it was mostly to play a bit with Airflow), but I find it pretty interesting on how the whole tool/paradigm kind of guides you into having a easily debuggable job:

  1. Since everything is a DAG, it feels a bit off to have just a single task, so you break your work in small tasks.
  2. But now you need to pass data between tasks, and the simplest way to do that is by having intermediate snapshots.
  3. And since you need to pick a name for the snapshots, it's quite intuitive to just add a timestamp, so you go for the nicely provided ds variable, which is the logical run date of the job (reproducible when you rerun the jobs, this is no "").

So now my old hacky shell script to notify me of free Steam games is now a fully reproducible pipeline with monitoring, logging and data snapshots. 🤯

Maybe now I'll find out why the script stopped working a while ago 😅

Today I was playing around with sprite stacks, which is something I wanted to do for a while.

It's so cool how easy it is to get something that looks "kind of 3D". Just make a quick model in MagicaVoxel, export to a sprite sheet and draw the sprites in order with some displacement depending on the camera position.

Even putting shadows on the ground is not that hard. It's kind of the same thing, but with a displacement based on height (instead of camera position).

Not sure if I'll do anything else with it, but it was fun. 🙂


After 6 months working on it, I finally released Minart 0.5.0-RC1, now with sound support. 🚀

This new version also drops 2.11 support, which was a pain to maintain.

I've been testing it with my previous entries and it seems to work pretty well. Once I've ported everything and am sure there are no obvious bugs I'll release the final version (and maybe write a blog post about it).

In the meantime, and unrelated to audio, this new version also comes with a bunch of performance improvements, so I can finally release Twotm8-native, an example GUI application in Scala Native. Check it out! 🙂

João Costa shared 10 months ago

So many cool news in Scala recently:

Scala 3.2.2 was just released and this time I'm in the contributor list 🎉. I wonder if a CSS change to scaladoc is enough for me to add "Compiler Engineer" to my CV 🤔.

Scala Native 0.4.10 and Scala JS 1.13.0 were also released recently, finally dropping 2.11 support. 🔥

Having both projects doing this at the same time is awesome! No weird cross-building problems for those who want to update (I was a bit scared that some libraries would rather drop Scala Native instead of 2.11) and it's a nice incentive for libraries to finally remove 2.11 support for good!

A timeline for reference:

  • 2.11.0 was released on Apr 17, 2014.
  • 2.12.0 was released on Nov 3, 2016 (6 years ago!).
  • 2.11.12 (the last 2.11 version) was released on Nov 9, 2017 (5 years ago).
  • Spark added 2.12 support on 2.4.0, which was released in Oct 29, 2018.
  • Scala native added 2.12 support in 0.4.0, released in Jan 19, 2021.

So it seems more than enough time for most applications to upgrade. 🙂

After 6 years I finally messed up this server in a way that I don't seem to be able to recover - partly my fault, but also partly due the booting logic that Scaleway used on this (now deprecated) instance type.

I was already constantly running out of memory anyway, so this might be a good time to upgrade. Still, just a heads up that federation with this instance might be a bit bumpy during the next week. 😬