TECH(K)NOW Day workshop on “Writing a programming language”

My OpenMarket colleagues and I ran a workshop at TECH(K)NOW Day on how to write your own programming language:

A big thank you to my colleagues from OpenMarket who volunteered to help: Rowan, Jenny, Zach, James and Elliot.

An extra thank you to Zach and Elliott for their impromptu help on the information desk for attendees:

Hopefully the attendees enjoyed it and learned a bit:

You can find the workshop slides, the full code, info about another simple language called Cell, and lots more links here:, my blog at, and follow me on twitter @andybalaam.

Thanks to OpenMarket for supporting us in running this workshop!

HTML5 CSS Toolbar + zoomable workspace that is mobile-friendly and adaptive

I have been working on a prototype level editor for Rabbit Escape, and I’ve had trouble getting the layout I wanted: a toolbar at the side or top of the screen, and the rest a zoomable workspace.

Something like this is very common in many desktop applications, but not that easy to achieve in a web page, especially because we want to take care that it adapts to different screen sizes and orientations, and, for example, allows zooming the toolbar buttons in case we find ourselves on a device with different resolution from what we were expecting.

In the end I’ve gone with a grid-layout solution and accepted the fact that sometimes on mobile devices when I zoom in my toolbar will disappear off the top/side. When I scroll back to it, it stays around, so using this setup is quite natural. On the desktop, it works how you’d expect, with the toolbar staying on screen at all zoom levels.

Here’s how it looks on a landscape display:

and portrait:

Read the full source code.

As you can see from the code linked above, after much fiddling I managed to achieve this with a relatively small amount of CSS, and no JavaScript. I’m hoping it will behave well in unexpected scenarios, because the code expresses what I want fairly closely.

The important bits of the HTML are simple – a main div, a toolbar containing buttons, and a workspace containing some kind of work:

<div id="main">
    <div id="toolbar">
    <div id="workspace">
        <div id="work">

The keys bits of the CSS are:

/* Ensure we take up the full height of the page. */
html, body, #main
    height: 100%;

@media all and (orientation:landscape)
    /* On a wide screen, it's a grid with 2 columns,
       and the toolbar can scroll downwards. */
        display: grid;
        grid-template-columns: 5em 1fr;
        overflow-x: hidden;
        overflow-y: auto;

@media all and (orientation:portrait)
    /* On a tall screen, it's a grid with 2 rows,
       and the toolbar can scroll right. */
        display: grid;
        grid-template-rows: 5em 1fr;
        overflow-x: auto;
        overflow-y: hidden;
        white-space: nowrap;

That replaces an awful lot of code in my first attempt, so I’m reasonably happy. If anyone has suggestions about how to make “100%” really mean 100% of the real device width and height, let me know. If I do some JavaScript I can make Mobile Firefox fit to the real screen size, but Mobile Chrome (and, I assume, Mobile Safari) lie to me about the screen size when zoomed in.

Broken Levels Challenge – Egham Raspberry Pi Jam July 2017

Today at the Egham Raspberry Pi Jam we did two things:

1. The Broken Levels Challenge

Some nasty person came and broke our levels for our game Rabbit Escape and we need you to fix them!

To play this game you will need a PC version of Rabbit Escape, our Broken Levels, and the instruction sheets. Let us know how you get on!

2. Python Traffic Lights Programming Workshop

I ran a workshop to learn a bit of Python programming using this resource sheet Pi Stop Traffic Lights.

We had a lot of fun, and hopefully some people even learnt a little bit of coding.

Women Who Code workshop on “Write your own programming language”

On Wednesday 28th June 2017 a group of people from OpenMarket went to the Fora office space in Clerkenwell, London to run a workshop with the Women Who Code group, who work to help women achieve their career goals.

OpenMarket provided the workshop “Write your own programming language” and funded the food, and the venue was provided gratis by Fora.

We started the evening with some networking and food:



but most of the time was spent coding:


with lots of help from our OpenMarket helpers:


The feedback we got was very positive:

Everyone seemed to be having fun, so we hope we might get invited back to do more in future.

Why do this?

At OpenMarket we want to improve our diversity, and we have started by looking at gender diversity specifically. By being involved with events like this we hope to learn how we can make our company better at welcoming and supporting employees, encourage people from under-represented groups to apply to work here, and improve the general climate in our industry.

Thank you

A huge thank you to the OpenMarket people (from London and Guadalajara!) who helped out – I think people felt welcome and there was plenty of help available for the attendees – you did a great job.

Thank you also for the great response from everyone in our London office – several people in the office wanted to come but couldn’t make it on the night – I am hoping we will get more opportunities in future.

We’re also really grateful to OpenMarket for funding the food, to Fora for providing the space, and to Women Who Code for doing such great work to improve our industry.


[Photos by David Lawson.]