a self-built Bubble Bobble bartop arcade machine

I like playing arcade games. I’ve had an “arcade” in my home town and I used to go there after school quite frequently. It was a small place – maybe 5 machines and some pinball machines.

In february this year it occured to be that with the power of the Raspberry Pi and a distribution called RetroPie I could build something that would bring back the games and allow me to play/try those games I never could because my arcade was so small back in the days.

To get a better idea of how to approach this I started to search around and found the build-log of Holbrook Tech where they’ve built a “Bigger Bartop Arcade”.

With their basic plans I started drawing in Inkscape and told my father about the plan. He was immediately in – as the plan now was to not build one but two bartop arcade machines. He would take the task of carrying out the wood works and I would do the rest – procurements, electronics, wiring, design and “painting”.

first drawings of the side panels

While I took the Holbrook Tech schematics as a base it quickly came apparent that I had to build/measure around the one fixed big thing in the middle: the screen.


I wanted something decently sized that the RaspberryPi would be able to push out to and that would require no maintenance/further actions when installed.

To find something that fits I had my requirements fixed:

  • between 24″ – 32″
  • colour shift free wide viewing angle
  • 1080p
  • takes audio over HDMI and is able to push it out through headphone jack

I eventually settled for a BenQ GW2780 27″ monitor with all boxes ticked for a reasonable price.

After the monitor arrived I carried it to my fathers house and we started to cut the bezel as a first try.

measuring the monitor in – on a piece of wood for testing.

After some testing with plywood we went for MDF as it was proposed by others on the internet as well. This made the cutting so much easier.


We went with standard 2cm MDF sheets and my father cut them to size with the measurements derived from the monitor bezel centerpiece.

Big thanks to my father for cutting so much wood so diligently! The next days he sent me pictures of what he’d made:

the plywood bezel was replaced with the MDF version
Each sheet of MDF wood got a steel screw thread insert. The screw is going on the inside through another peice of wood which is screwed and glued directly to the insides. This holds everything firm and is invisible from the outsides.
The only screws visible from the outside are holding the back panel on. Because you need to be able to remove the back panel they can be removed. Also the back panel is plit into two parts because that gave more structural strength and helps with the power input mounting later.
I went for Joystick + 6-Button layout for the control panel. I’ve changed the measurements a bit over the ones I’ve found on the internet to my taste.
The above schematics show the actual measured holes as they were drilled. As everything went more or less “free-hand” it’s quite astonishing to me how accurate it went. This measurement schematic was later used to laser cut the acrylic handrest.

The side panels got a cut around for the black T-Molding to be added later.

electronics and wiring

After about 2 weeks my father had built the first arcade out of sheets of MDF and I had taken delivery of the remaining pieces of hardware I had ordered after making a long list.

The most interesting parts of the above list might be the 2-player joystick + buttons + encoder set.

It contains 2 standard 4/8-way switchable arcade joysticks, 10 buttons, all microswitches required and the Ultimarc I-PAC-2 joystick encoder.

You connect every microswitch to this board and it will translate all button presses/joystick movements into keyboard or joystick movements. You connect it through USB to the RaspberryPi and it either shows up as 2 gamepads or one keyboard. Also a nice configuration app is available from the manufacturer.

So when I got the first arcade from my father I started to put in the electonics immediately.

The wiring to the I-PAC was straight forward. Worked at the first try.

The sound was a bit more complicated. I wanted a volume control knob on the outside but also did not want to disassemble any audio amplifier.

I went with the simplest solution: A 500k Ohm dual potentiometer soldered into the headphone extension cable going to the amplifier. The potentiometer then got put into a pot and a whole made it stick out so that a knob could be attached.

The RaspberryPi set-up then only lacked cooling. The plan was to put a 120mm case fan to pull in air from the bottom and went it out another 120mm case hole at the upper back. Additionally the RaspberryPi would get it’s own small 30mm fan on top of it’s heatsink case.

I attached both fans directly to the RaspberryPi – so I saved myself another power supply.


Now I had to make it all work together. As I wanted to use RetroPie in the newest 4.6 release I’ve set that up and hooked it all up.

On first start-up EmulationStation asked me to configure the inputs. It had detected 2 gamepads as I had put the IPAC-2 into gamepad mode before. You can do this with a simple mode-switch key-combination that you need to hold for 10 seconds to make it switch.

The configuration of the buttons of the two players went without any issue. First I had set-up the player 1 input. Then I re-ran the input configuration again for player 2 inputs.

The controls where straight forward. I wanted mainly 4-way games but with enough buttons to switch to some beat-em-ups at will.

So I configured a simple layout into Retroarch with some additional hotkeys added:

vinyl design

I tossed around several design ideas I had. Obviously derived from those games I wanted to play and looked forward to.

There was some Metal Slug or some Cave shooter related designs I thought of. But then my wife had the best ideas of them all: Bubble Bobble!

So I went and looked for inspiration on Bubble Bobble and found some but none that sticked.

There was one a good inspiration. And I went to design based upon this one – just with a more intense purple color scheme.

I used Inkscape to pull in bitmap graphics from Bubble Bobble and to vectorize them one by one, eventually ending up with a lot of layers of nice scalable vector graphics.

With all design set I went and sliced it up and found a company that would print my design on vinyl.

With the final arcade-wood accessible top me I could take actual measurements and add to each element 4cm of margin. This way putting it on would hopefully be easier (it was!).

Originally I wanted to have it printed on a 4m by 1,2m sheet of vinyl. It all would have fit there.

But I had to find out that Inkscape was not capable of exporting pixel data at this size and a pixel-density of 600dpi. It just was too large for it to output.

So I had to eventually cut all down into 5 pieces of 1,2m by 80cm each.

After about 7 days all arrived printed on vinyl at my house. I immediately laid everything out and tried if it would fit. It did!

Now everything had to go onto the wood. I did a test run before ordering to check if it would stick securely to the wood. It did stick very nicely. So putting it on was some intense fiddling but it eventually worked out really really great.

You can see the inside here and the structural struts where everything attaches to screwed in from the insides.

Now it was time for some acrylic. I wanted to get a good bezel and covering of the monitor as well as the handrest and the front buttons.

Cutting acrylic myself was out of questions – so I went with a local company that would laser-cut acrylic for me to my specification.

I’ve sent them the schematics and measurements and the panels for reference and 4 days later the acrylic arrived. We could then put the last bits together for completion!


I am really happy how this turned out – especially since with everything that required actual work with hands I am a hopeless case. With this somehow everything worked out.

I still employ the idea of a vertical shoot-em-up centered version… but maybe some day.

If you got any questions or feedback let me know!

Neumorphism is upon us!

After the demise of Skeuomorphism and material-design there’s a new kid on the block to take the trophy: Neumorphism!

Neumorphic card however pretends to extrude from the background. It’s a raised shape made from the exact same material as the background. When we look at it from the side we see that it doesn’t “float”.


As you might have noticed I have already switched the drop-shadows on this blogs theme to also use this very simple shadow-recipe.

And if you want to – you can go here and generate all you need in a handy configurator:

German Train Network Plans

Apparently the german main train operator does offer their regional and nationwide train network in an overall one-pager plan version:

Now, if you take the nationwide one, it looks like this:

It looks okay, but not that great. Given the many examples of proper train network plans.

Someone as well was not satisfied, so this person created one and put it on reddit:

This is so much nicer! Of course this has to be taken with the addition of: there are several “jokes” hidden in the names and lines. Don’t take this as an actual reference – rather go by the official ones.

generative art: flowers

It started with this tweet about someone called Ayliean apparently drawing a plant based upon set rules and rolling a dice.

And because generative art in itself is fascinating I am frequently pulled into such things. Like this dungeon generator or these city maps or generated audio or face generators or buildings and patterns

On the topic of flowers there’s another actual implementation of the above mentioned concept available:

Drawing Transit Maps

Almost exactly 1 year ago I wrote about transit maps. And it seems to be a recurring topic. And rightfully so – it’s an interesting topic.

Along the presentation of a redesigned Singapore transit map, there’s more content to gather on the “Transit Mapping Symposium” website.

The “Transit Mapping Symposium” will take place in Seoul / South-Korea on 20/21st of April 2020 with researchers and designers meeting up.

The Transit Mapping Symposium is a yearly international gathering of transport networks professionals, a unique opportunity to share achievements, challenges and vision.

Our participants and speakers include experts from all fields of the industry:

– Mapmakers
– Network Operators
– Transport Authorities
– Digital Platforms
– Designers

Blender 3D – December was full of content

So with the new year started it might be worth looking into some patterns different from the ones we are usually dealing with. So how about a bit of 3D graphics, shaders and modelling?!

Get your gear:

Blender is the free and open source 3D creation suite. It supports the entirety of the 3D pipeline—modeling, rigging, animation, simulation, rendering, compositing and motion tracking, video editing and 2D animation pipeline.


And then get a starting point. Be quick, as this is on Twitter it might fade away:

There’s so much interesting stuff in there – and lots to learn!

a proper 7-segment / 14-segment font

DSEG is a free font family, which imitate seven and fourteen segment display(7SEG,14SEG). DSEG have special features:

  • DSEG includes the roman-alphabet and symbol glyphs.
  • More than 50 types are available.
  • True type font(*.ttf) and Web Open Type File Format (*.woff, *.woff2) are in a package.
  • DSEG is licensed under the SIL Open Font License 1.1.

Get it here.

procedurally generated cities

This application generates a random medieval city layout of a requested size. The generation method is rather arbitrary, the goal is to produce a nice looking map, not an accurate model of a city. Maybe in the future I’ll use its code as a basis for some game or maybe not.

Medieval Fantasy City Generator

a 1980s style computer built today for fun

Can you display VGA and play audio on a Cortex-M4 in pure Rust? The short answer is yes, yes you can! Minus the hand-unrolled assembler loop for fixing the phase error in the RGB output. But we don’t talk about that in polite company.

Monotron project page

What currently is in place:

  • The Atari Joystick interface works, but two Joysticks would be more fun
  • The PS/2 Keyboard via the Atmega works, but the pinout was mirrored so you have to put the connector under the PCB :/
  • The RTC works
  • VGA Output works
  • The MIDI Out seems to work when looped to MIDI In, as does the MIDI Though.
  • The MIDI In seems to receive data when connected to my electronic drum kit
  • The Audio output seems to work quite nicely
  • The SD card works, but the power supply can’t handle hot-insertion of the SD card and it makes the TM4C reboot. More capacitors / some current limiting probably required.

I can load games and programs from the SD card into the 24 KiB of free Application RAM. You can interact with these games via the PS/2 Keyboard and Joystick. I can play simple games (like Snake) and play three channels of 8-bit wavetable audio simultaneously. I’ve even got a 6502 Emulator running a copy of 6502 Enhanced BASIC, if you want to go old school!

ASCII browser games

A lot is going on in browsers these days. They are becoming increasingly powerful and resource-demanding.

So it just feels natural to combine high resource usage infrastructure with low resource using graphics to get the worst of both worlds.

Not quite, but you get the idea.

There’s a guy on the internet (haha) who dedicates time to write ASCII / character based graphics engines and games with it.

Meet MrGumix:

Of course, what’s that games and graphics?

Exhibit #1:

And the more advanced Exhibit #2:

C# PlayStation emulation

After looking into the NES emulation written entirely in C# I came across a similar approach using C# to emulate a full and much more complex PlayStation 1.

Scott Hanselman wrote:

I then stumbled on this very early version of a PSX Emulator in C#.

Now, if you were to theoretically have a Playtation SCPH1001.BIN BIOS and then physically owned a Playstation (as I do) and then created a BIN file from your physical copy of Crash Bandicoot, you could happily run it as you can see in the screenshot below.

AR use-case: Motorcycle Helmet

I do not drive motor cycles. I never found a reason to.

Given that non-experience: I can only assume that something like this helmet would really make a difference for bikers.

With the integrated camera system it will have a rear-view mirror screen in sight all the time and be able to overlay all sorts of information into the field-of-view of the driver. In addition it seems to be capable to augment the audio getting to the driver in various ways.

If you are as interested as I am, despite not having a motorcycle: take a look at the Indiegogo campaign.

Fonts for Coders: Cascadia

Microsoft recently is releasing a lot of tools and assets for developers and terminal monkeys.

This is good. Very nice of them.

The recent release of a font specifically for terminal and code editing use seems worth a mention here:

Cascadia Code was announced this past May at Microsoft’s Build event. It is the latest monospaced font shipped from Microsoft and provides a fresh experience for command line experiences and code editors. Cascadia Code was developed hand-in-hand with the new Windows Terminal application. This font is most recommended to be used with terminal applications and text editors such as Visual Studio and Visual Studio Code.

Cascadia Code announcement

What’s most interesting about this: It’s got code ligatures. Just recently a lot of development focussed fonts showed up and they started to incorporate special characters for development specific character combinations:

Cascadia Code supports programming ligatures! Programming ligatures are most useful when writing code, as they create new glyphs by combining characters. This helps make code more readable and user-friendly for some people.


Wave Function Collapse

I’ve written on this topic before here. And as developers venture more into these generative algorithms it’s all that more fun to see even the intermediate results.

Oskar Stålberg writes about his little experiments and bigger libraries on Twitter. The above short demonstration was created by him.

Especially worth a look is the library he made available on GitHub: mxgmn/WaveFunctionCollapse.

Some more context, of questionable helpfulness:

In quantum mechanicswave function collapse occurs when a wave function—initially in a superposition of several eigenstates—reduces to a single eigenstate due to interaction with the external world. This interaction is called an “observation”. It is the essence of a measurement in quantum mechanics which connects the wave function with classical observables like position and momentum. Collapse is one of two processes by which quantum systems evolve in time; the other is the continuous evolution via the Schrödinger equation. Collapse is a black box for a thermodynamically irreversible interaction with a classical environment. Calculations of quantum decoherence predict apparent wave function collapse when a superposition forms between the quantum system’s states and the environment’s states. Significantly, the combined wave function of the system and environment continue to obey the Schrödinger equation.

Wikipedia: WFC

Right. Well. Told you. Here are some nice graphics of this applied to calm you:

Convert HEIC to JPEG or PNG

If you own a modern age phone it’s very likely that it will store the photos you take in a wonderful format called HEIC – or “High Efficiency Image File Format (HEIF)”.

Now the issue with this format is that your average toolchain is based upon things like Portable Network Graphics (PNG), JPEG and maybe GIF or Scalable Vevtor Graphics (SVG).

So HEIC does not quite fit yet. But you can make it fit with this on Linux.

Imagemagick and current GIMP installations apparently still don’t come pre-compiled with HEIF support. But you can install a tool to easily convert an HEIC image into a JPG file on the command line.

apt install libheif-examples

and then the tool heif-convert is your friend.

2001-era docomo flip phone emoji font

NTT DoCoMo might not have been the first ones to release feature phones with actual emoji characters to be used in text messaging. But their set of original emojis is just oh-so-beautiful to look at.

With the help of Monica Dinculescu we now can enjoy these emojis on our modern era computing machines.


You can either get the font downloaded for free directly from Monicas page or you could use her SVG code to further make use of the great emojis.

the font download will get you this

If you go for the SVG link you will get some overview alike the one at the start of this post. If you wanted to further work with the raw vector data (SVG) in there you could use this simple trick:

Step 1: locate the emoji you want in the code of the page. Maybe by utilizing the developer tools of your browser.

Step 2: Copy that specific element that you want to your clipboard / into a new text document.

Step 3: add the proper header tag before the element you’ve copied.

<?xml version="1.0" encoding="utf-8"?>

Step 4: Save the contents now as a file with the .svg ending. You can now open it up in any SVG compatible editor, like Inkscape.

Homebrew AR: HoloKit

Augmented Reality – AR – is getting some buzz here and there throughout the last 20 years almost. With hardware becoming more powerful and optics+light hardware becoming cheaper and more efficient it’s still all but close to become widely used and available.

Many refer to some one-trick pony feature in location-based games like “Pokemon Go” to being “AR”. But actual useful cases of AR are there but not feasible with current hardware generations.

Nevertheless a team in california has taken our the scissors and keyboards and made HoloKit:

HoloKit features super sharp optics quality and a 76-degree diagonal field of view. Pairing with a smartphone, HoloKit can perform an inside out tracking function, which uses the changing perspective on the outside world to note changes in its own position. HoloKit merges the real and the virtual in a smart way. While you see through the real world, virtual objects are blended into it. Powered by the accurate gyro and camera on smart phones, HoloKit solidly places virtual objects onto your table or floor, as if they were physically there without physical makers. These virtual objects will stay in the same place even if you walk away, just like real physical objects.

HoloKit is different from screen-based AR experience like Tango. You can directly see through the headset and view the real world as is, and in the meantime the virtual objects are projected on top of the real world, as opposed to viewing both the real and the virtual through a smartphone camera.


create 3D environments with your phone – early access

Augmented Reality needs proper 3D geometry and the ability to sense the environment to interact with it. At some point I would expect tools to show up that allow us to do some of this ourselves.

Seems like we’re one step closer. Ubiquity6 is reaching out to get early access to interested users:

We’re giving early access to our 3D mapping tools for creators and artists! If you’re interested in trying it out sign up for early access here: https://ubiquity6.typeform.com/to/bmpbkB

Ubiquity6 on Twitter

Of course. I applied. And I’ve just started testing.

color assimilation grid illusion

The image [..] is a visual/artistic experiment playing with simultanous contrast resulting from other experiments these days. An over-saturated colored grid overlayed on a  grayscale image causes the grayscale cells to be perceived as having color.
The processing needed to create the above image happened along with unrelated but significant code improvements In the last couple of weeks. I have been visiting mitch – a prolific GIMP contributors for collaboration – and lots of progress has been – and is still – being made on babl, GEGL and GIMP.

original article
See the effect in a video

You can now play with this effect and experiment for yourself. Get Gimp and enjoy!

easily draw text based flowcharts

As I am mainly producing text and markdown notes throughout the day I am always interested in ways to quickly create simple text-based flow-charts.

I did write about a couple of tools to accomplish this previously but I want to take note of the most recent addition to the toolbox: ASCIIFlow Infinity.

You open it in your browser and start drawing with the simple tools provided.

When you are done you export it to plain text and do what you feel like with it.

Here’s a feature overview:

a wild Ma.K (Maschinen Krieger) appears

The franchise was started by Kow Yokoyama in the 1980’s. Yokoyama-san was a scratch-build modeller, artist and sculptor. Among his works he built machines of war that would fight in the 29th century, but took their visual cues from early 19th century weaponry and the early NASA space program. All his models were pieced together from numerous kits including armor, aircraft, cars and found objects (like ping pong balls).


Often described as WWII machinery in space, these kits are the perfect blend of sci-fi modelling with AFV weathering and finishing techniques…

There is also a longer article with high-resolution pictures here.

TAICHI: opensource computer graphics library

I am following the proceedings of ACM SIGGRAPH conferences for more than 20 years now and with the recent years development in computational capacity it seems that many more algorithms and ideas make it to an application near you.

Take this one contribution by Yuanming Hu for example – the Taichi open source computer graphics library:

Taichi is an open-source computer graphics library that aims to provide easy-to-use infrastructures for computer graphics R&D. It’s written in C++14 and wrapped friendly with Python.

Yuanming Hu has been working on the development of Taichi since his third undergrad year (2016), mainly in his spare time. He would like to thank Prof. Toshiya Hachisuka and Prof. Seiichi Koshizukafor making possible his internship at UTokyo, where the initial parts of Taichi were developed.

Taichi: About

Also interesting, trivia about the name:

augmented (reality) book cover

If you ever want to quickly explain what augmented reality could be to a person not knowing yet, you might want to use this (and other) use cases for a visual explanation:

I achieved this by separating the artwork and text into many individual layers, that I placed in receding layers of 3D depth, in a 3D program on the computer. And made sure everything outside the borders of the book is excluded, to give it the ‘portal’ effect.

Augmented Reality Book Cover by Alexander Wand