Lunar Lander

Just want to play my game without reading this whole post? Play the game here – press a key, mouse button, or touch the screen to fire the thrusters, and try to land at less than 4 m/s with as much fuel left over as possible.

In 1969, when all the nerds were still excited by sending humans to the moon instead of flinging cars around the sun, the hottest video game was Rocket (or Lunar) for the PDP-8. Originally implemented in FOCAL by high school student Jim Storer and soon afterwards ported to BASIC (the other dominant language to come as standard with microcomputers), Rocket became the precursor to an entire genre of video games called “Lunar Lander games“.

Source code of Rocket and sample output.
Like many pieces of microcomputer software of the time, Rocket was distributed as printed source code that you’d need to carefully type in at the other end.

The aim of these games was to land a spacecraft on the moon or similar body by controlling the thrust (and in some advanced versions, the rotation) of the engine. The spacecraft begins in freefall towards the surface and will accelerate under gravity: this can be counteracted with thrust, but engaging the engine burns through the player’s limited supply of fuel. Furthermore, using fuel lowers the total mass of the vessel (a large proportion of the mass of the Apollo landers was fuel for use in the descent stage) which reduces its inertia, giving the engine more “kick” which must be compensated for during the critical final stages. It sounds dry and maths-y, but I promise that graphical versions can usually be played entirely “by eye”.

Atari's Lunar Lander (1979)
Atari’s 1979 adaptation is perhaps the classic version you’d recognise, although its release was somewhat overshadowed by their other vector-graphics space-themed release in 1979: Asteroids.

Let’s fast-forward a little. In 1997 I enrolled to do my A-levels at what was then called Preston College, where my Computing tutor was a chap called Kevin Geldard: you can see him at 49 seconds into this hilariously low-fi video which I guess must have been originally shot on VHS despite being uploaded to YouTube in 2009. He’s an interesting chap in his own right whose contributions to my career in computing deserve their own blog post, but for the time being all you need to know is that he was the kind of geek who, like me, writes software “for fun” more often than not. Kevin owned a Psion 3 palmtop – part of a series of devices with which I also have a long history and interest – and he taught himself to program OPL by reimplementing a favourite game of his younger years on it: his take on the classic mid-70s-style graphical Lunar Lander.

Psion Series 3
I never owned a Psion Series 3 (pictured), but I bought a Series 5mx in early 2000 out of my second student loan cheque, ultimately wrote most of my undergraduate dissertation using it, and eventually sold it to a collector in about 2009 for almost as much as I originally paid for it. The 5mx was an amazing bit of kit. But I’ll blog about that another day, I guess.

My A-level computing class consisted of a competitive group of geeky lads, and we made sort-of a personal extracurricular challenge to ourselves of re-implementing Kevin’s take on Lunar Lander using Turbo Pascal, the primary language in which our class was taught. Many hours out-of-class were spent in the computer lab, tweaking and comparing our various implementations (with only ocassional breaks to play Spacy, CivNet, or my adaptation of LORD2): later, some of us would extend our competition by going on to re-re-implement in Delphi, Visual Basic, or Java, or by adding additional levels relating to orbital rendezvous or landing on other planetary bodies. I was quite proud of mine at the time: it was highly-playable, fun, and – at least on your first few goes – moderately challenging.

Dan's Lunar Lander (2018)
I sometimes wonder what it would have looked like if I’d have implemented my 1997 Lunar Lander today. So I did.

Always game to try old new things, and ocassionally finding time between the many things that I do to code, I decided to expand upon my recently-discovered interest in canvas coding to bring back my extracurricular Lunar Lander game of two decades ago in a modern format. My goals were:

  • A one-button version of a classic “straight descent only” lunar lander game (unlike my 1997 version, which had 10 engine power levels, this remake has just “on” and “off”)
  • An implementation based initially on real physics (although not necessarily graphically to scale)… and then adapted as necessary to give a fun/playability balance that feels good
  • Runs in a standards-compliant browser without need for plugins: HTML5, Canvas, Javascript
  • Adapts gracefully to any device, screen resolution, and orientation with graceful degredation/progressive enhancement

You can have a go at my game right here in your web browser! The aim is to reach the ground travelling at a velocity of no more than 4 m/s with the maximum amount of fuel left over: this, if anything, is your “score”. My record is 52% of fuel remaining, but honestly anything in the 40%+ range is very good. Touch the screen (if it’s a touchscreen) or press a mouse button or any key to engage your thrusters and slow your descent.

End point of Dan's Lunar Lander (2018)
“Houston, the Eagle has landed.” Kerbal Space Program, it isn’t. Here’s a very good landing: 3 m/s with 48% of the fuel tank remaining.

And of course it’s all open-source, so you’re more than welcome to take it, rip it apart, learn from it, or make something better out of it.

Report: 80’s kids started programming at an earlier age than today’s millennials

Report: 80's kids started programming at an earlier age than today's millennials by Matthew Hughes (The Next Web)
Thanks BBC Micro!

HackerRank has published its 2018 Developer Skills Report. The paper looks at a number things essential to understanding the developer landscape, and explores things like the perks coders demand from their workplaces, the technologies they prefer to use, and how they entered the software development industry in the first place.

While perusing the paper, something struck me as particularly interesting. One of the questions HackerRank asked its community was when they started coding. It then organized the data by age and country.

Almost immediately, you notice an interesting trend. Those in the 18 to 24 age group overwhelmingly started their programming journey in their late teens. 68.2 percent started coding between the ages of 16 to 20.

When you look at older generations, you notice another striking trend: a comparatively larger proportion started programming between the ages of five and ten. 12.2 percent of those aged between 35 and 44 started programming then.

It’s obvious why that is. That generation was lucky enough to be born at the start of the home computing revolution, when machines bearing the logos of Acorn and Commodore first entered the living rooms of ordinary people.

This survey parallels my own experience: that among developers, those of us who grew up using an 80s microcomputer at home were likely to have started programming a decade or so younger than those who grew up later, when the PC had come to dominate. I’ve written before about why I care about programming education, and I still think that we’re not doing enough to show young learners what’s “under the bonnet” of our computer systems. A computer isn’t just a machine you can use, it’s a tool you can adapt: unlike the other machines you use, which are typically built to a particular purpose, a computer is a general-purpose tool and it can be made to do an infinite number of different tasks! And even if programming professionally isn’t “for you” (and it shouldn’t be for everyone!), understanding broadly how a tool – a tool that we all come into contact with every single day – is adapted makes us hugely better-able to understand what they’re capable of and pushes us forwards. Imagine how many young inventors would be able to realise their for the “killer app” they’ve dreamed up (even if they remained unable to program if themselves) if they were able to understand the fundamental limtations and strengths of the platforms, the way to express their idea unambiguously in a way that a programmer could develop, and the way to assess its progress without falling into the “happy path” testing problem.

I’m not claiming that late-Gen X’s are better programmers than Millenials, by the way: absolutely not saying that! I’m saying that they were often lucky enough to be shaped by an experience that got them into programming earlier. And that I wish we could find a way to offer that opportunity to today’s children too.

How it feels to learn JavaScript in 2016

How it feels to learn JavaScript in 2016 – Hacker Noon (

No JavaScript frameworks were created during the writing of this article.

The following is inspired by the article “It’s the future” from Circle CI. You can read the original here. This piece is just an opinion, and like any JavaScript framework, it shouldn’t be taken too seriously.

Hey, I got this new web project, but to be honest I haven’t coded much web in a few years and I’ve heard the landscape changed a bit. You are the most up-to date web dev around here right?

-The actual term is Front End engineer, but yeah, I’m the right guy. I do web in 2016. Visualisations, music players, flying drones that play football, you name it. I just came back from JsConf and ReactConf, so I know the latest technologies to create web apps.

Cool. I need to create a page that displays the latest activity from the users, so I just need to get the data from the REST endpoint and display it in some sort of filterable table, and update it if anything changes in the server. I was thinking maybe using jQuery to fetch and display the data?

-Oh my god no, no one uses jQuery anymore. You should try learning React, it’s 2016.

Oh, OK. What’s React?

A year or two old, and I’d love to claim that things were better in Javascript-framework-land today… but they’re not.

git git git git git

Ever found you’ve accidentally entered too many gits in your terminal and wondered if there’s a solution to it? I quite often type git then go away and come back, then type a full git status after it. This leads to a lovely (annoying) error out the box:

$ git git status
git: 'git' is not a git command. See 'git --help'.

What a git.

My initial thought was overriding the git binary in my $PATH and having it strip any leading arguments that match git, so we end up running just the git status at the end of the arguments. An easier way is to just use git-config‘s alias.* functionality to expand the first argument being git to a shell command.

git config --global alias.git '!exec git'

Which adds the following git config to your .gitconfig file

  git = !exec git

And then you’ll find you can git git to your heart’s content

$ git sha

$ git git sha

$ git git git git git git git git git git git git git git git git git git git git git git git git git git sha

(git sha is an alias for git rev-parse HEAD.)

See what other git alias’ I have in my ~/.gitconfig, and laugh at all the typo corrections I have in there. (Yes, git provides autocorrection if you enable it, but I’m used to these typos working!)

Now git back to doing useful things!

Why I Still Use Vim

I often get asked about why I use Vim as my primary editor, there is no particular reason for this, except that I ended up learning it when I moved over to Linux full time many years ago. I ended up liking it because I could edit my small source files on my quad-core machine without needing to wait forever for the file to open.

Keyboard with Vim keycaps

Sure Vim isn’t a bad editor, it’s highly extensible, it’s easy to shell out to the, err well shell, its everywhere so when you ssh into some obscure server you can just type vim (or vi) and you’re good to go…

Engineering Empathy

This was a talk I gave at an internal R&D conference my last week at Workiva. I got a lot of positive feedback on the talk, so I figured I would share it with a wider audience. Be warned: it’s long. Feel free to read each section separately, though they largely tie together.

Why do you work where you work? For many in tech, the answer is probably culture. When you tell a friend about your job, the culture is probably the first thing you describe. It’s culture that can be a company’s biggest asset—and its biggest downfall. But what is it?

Culture isn’t a list of values or a mission statement. It’s not a casual dress code or a beer fridge. Culture is what you reward and what you don’t. More importantly, it’s what you reward and what you punish. That’s an important distinction to make because when you don’t punish behavior that’s inconsistent with your culture, you send a message: you don’t care about it…

Why it is just lazy to bad-mouth Ruby on Rails

It’s inevitable these days: we will see an article proclaiming the demise of Ruby on Rails every once in a while. It’s the easiest click bait, like this one from TNW.Now, you may say “another Ruby fanboy.” That’s fair, but a terrible argument, as it’s a poor and common argumentum ad hominem. And on the subject of fallacies, the click-bait article above is wrong exactly because it falls for a blatantly Post hoc ergo propter hoc fallacy plus some more confirmation bias which we are all guilty of falling for all the time.

I’m not saying that the author wrote fallacies on purpose. Unfortunately, it’s just too easy to fall for fallacies. Especially when everybody has an intrinsic desire to confirm one’s biases. Even trying to be careful, I end up doing that as well…

You Are Not Google – Bradfield

Software engineers go crazy for the most ridiculous things. We like to think that we’re hyper-rational, but when we have to choose a technology, we end up in a kind of frenzy — bouncing from one person’s Hacker News comment to another’s blog post until, in a stupor, we float helplessly toward the brightest light and lay prone in front of it, oblivious to what we were looking for in the first place.

This is not how rational people make decisions, but it is how software engineers decide to use MapReduce…

What Happens When You Mix Java with a 1960 IBM Mainframe

IBM Mainframe

As an engineer for the U.S. Digital ServiceMarianne Bellotti has encountered vintage mainframes that are still being used in production — sometimes even powering web apps. Last month she entertained a San Francisco audience with tales about some of them, in a talk called “7074 says Hello World,” at Joyent’s “Systems We Love” conference.

Created under the Obama administration, The U.S. Digital Service was designed as a start-up-styled consultancy to help government agencies modernize their IT operations, drawing engineering talent from Google, Facebook and other web-scale companies.

Or, as President Obama put it last March, it’s “a SWAT team — a world-class technology office.”

So it was fascinating to hear Bellotti tell stories about some of the older gear still running, and the sometimes unusual ways it was paired with more contemporary technology…

A Constructive Look At TempleOS

TempleOS is somewhat of a legend in the operating system community. Its sole author, Terry A. Davis, has spent the past 12 years attempting to create a new operating from scratch. Terry explains that God has instructed him to construct a temple, a 640×480 covenant of perfection. Unfortunately Terry also suffers from schizophrenia, and has a tendency to appear on various programming forums with a burst of strange, paranoid, and often racist comments. He is frequently banned from most forums