Kilian Valkhof

Front-end & user experience developer, Jedi.

The box model is not layout

Design, 8 October 2019

One term that keeps coming up in the design community as a stand-in for layout is “box model”, for example in “Why don’t design tools have the box model?” The CSS Box model is a well-defined term though, and it does not do layout.

If we keep referring to our imaginary perfect layout system in design tools as “box model”, we risk getting the wrong thing.

Superposition: use the design system you already have

Design, 13 August 2019

Having a design system is like having a super power. It takes away all the small decisions you have to make about a design and lets you focus on the higher level goals you have for your design. But creating a design system is a labour intensive process usually only worth it for product teams at large companies or startups.

Notarizing your Electron application

Electron, 4 June 2019

Starting with MacOS 10.14.5, all signed applications by ‘new’ developers will need to be notarized or they will trigger Apple’s Gatekeeper software and prevent users from installing your app. That means that aside from signing your application, you will need to notarize it as well. This is how to successfully notarize your Electron application.

Polypane available now

Apps, 14 May 2019

Polypane is out today! Polypane is a browser for developers, designers and everyone else that creates websites and webapps. This release has been a long time in the making, and has taken a lot of hard work in the past months to get this release out the door. I am incredibly proud of the app I’ll be sharing with all of you today.

Getting Polypane ready for release

Apps, 30 April 2019

In a few weeks, Polypane version 1.0 will be released. In these past few months I’ve been hard at work getting everything ready for that release. 

The process has very little to do with the app itself and much more with creating the infrastructure around it. I thought it would be interesting to go through this to show you what it takes.

Polypane browser for responsive web development and design Hi, I'm Kilian. I make my living building Polypane, the browser for responsive web development and design. If you're reading this site, that's probably interesting to you. Please try it out!

I develop more software and tools:


Use the design system you already have


A cross-platform, simple and smart autosaving scratchpad.

A Messenger Adventure!

Go on a text adventure in Facebook Messenger.


The latest Electron news, articles, apps and interviews.


Drag-and-drop lossless compression of PNG and JPG images for web.

Messenger Demo Viewer

Demo your (bot) interactions on Messenger.