MOOC Review: Programming in Scratch

Course Title: CS002x Programming in Scratch
Provider: Harvey Mudd College via edX
Price: Free
Level: Introductory (suited to children)
Effort: 6 hours per week for 6 weeks, commencing on a set date
Prerequisites: None
Completion awards: Verified Certificate for USD$49

About the course:
This is not at all a bad course.  It’s well-suited to children, or really just about any ability level.  The children do need to be able to understand a fair amount of logic.  It’s a bit much for my 6-year-old son, even though he enjoys using Scratch.  (His ability level is simply knowing that command blocks are instructions for sprites, and lists of command blocks can be strung together.)

The course is described as a computer science course, but I really can’t feel like that’s justified. It’s a tour of Scratch’s capabilities, but doesn’t often describe theory or reasons for much.  There is an excellent amount of work with iteration, however.  One brief section also compares Scratch to industry standard programming languages, to show how the learning can be applied outside the Scratch environment.

Aside from it using Scratch, there was no prior indication that it was aimed at children, which it really is.  As Open University’s TU100 uses Sense, an off-shoot of pre-1.4 Scratch, there’s no reason to believe that a computer science course which uses Scratch must be a de facto children’s course.  There were plenty of students across many abilities and ages, so the discussion forums were a bit uneven at best.

The tour of Scratch begins with Scratch as the idealogical descendant of Logo incorporating a turtle graphics system.  This was bizarrely effective, because I was able to recall line-for-line programmes I wrote in Logo back in 1986 or ’87 after two weeks of lessons during elementary maths.  I reproduced it with just the addition of colour.

It winds past variables, iteration (as mentioned above), input, sprite-interaction, if-then-else logic, more iteration, functions, external calls, and even implies recursion with sprite clones.  Okay, for me, it took about 10 or 11 hours to get through everything but the final project, but that’s quite a list, and I can easily see it taking a young student a few weeks to get through that all.  But they will get through it all.  It’s all very logically laid out, it’s interesting, fun, and cool to keep them engaged, there are always lots of examples, and the progress made is a great confidence builder.

One confusing aspect is that the course has been adapted from some other curriculum, so it occasionally refers to weeks or other structures not present in the online, self-paced course.  It’s easy enough to ignore, but raises questions of how thoroughly prepared it is.

Two questions you might have for me are why did I take it, and what did I learn.

As stated, TU100 at the Open University, my first degree course module, uses Sense, which is based on Scratch.  Though I’ve played with Scratch before, and been impressed by it, I haven’t done anything in depth with it.  I was unaware of its true capabilities.  In a way, it’s a bit of a tragedy that I did that.

Scratch 1.6 is amazing.  It has functions, clones, lists, recursion … It’s great.  Sense, based on 1.4 or before, does not have clones, has no in-built stack for handling recursion data, and has to use calls for functions.  It appears as though it does have lists, in a custom solution.  I haven’t used it yet, so I’m still not sure.  I’m just lamenting that if I want to do recursion, I’ll have to use those lists to build my own stack.  Every. Single. Time.

And what did I learn?  Plenty!  One of my favourite moments was when I was polishing up my final project, and I wanted a custom score counter.  I searched the Internet for a Scratch solution, but couldn’t find anything that worked the way I wanted.  The closest I found was one which had a pre-set number of digits, with a separate sprite for each digit.  I realised that I could use recursion to call new clones of a single sprite to dynamically create as many digits as I wanted.

Another great moment is when I wanted to re-write a Rock-Paper-Scissors demo to include Rock-Paper-Scissors-Lizard-Spock.  The course wanted an If statement for each of the possible outcomes.  With Rock-Paper-Scissors, that’s just 6 possibilities.  With Spock and Lizard in the mix, it goes up to 15, and that’s already annoying.  So I diagrammed out the possibilities, saw a pattern, applied some modal maths, and realised there were really only three possible outcomes after said application.

So here are a couple of the things I created.  You can look inside any of the programmes to see how I did them, keeping in mind that I was learning as I went, so it’s not always the most logical way in the simpler programmes.

Jet Bike Steve: You Win Some, You Jetsam (Final project) WASD or arrow keys, up, W, or space to fire. 10 points per second survived, 10 points per star shot or collected, 25 points per bomb shot, and 50 points per guided-missile shot.

Derpa Deadfish (a game for my oldest boy)  You can go down, right, or left, but can only float up. Collect worms, avoid sharks (or turn them off), and use the safe-zone pad at the bottom.

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