## Introduction: Cellular Automaton Design for Cross-Stitch IPhone Case

Here you will find the design (and the source code for it) that I decided on for my DIY iPhone 4 case, as well as some tips and tricks on how to do a clean (and knot-free!) needle-point project that looks cool too.

Background
About a year and a half ago (July 2011) Make:Blog and Design Milk both highlighted an iPhone Case that doubles as a cross-stitch or needle-point canvas.  I had been itching to do something with my hands since I've been busy enough not, and thought this would be a quick and fun project to dive into.

I was right!  However, while fun and straightforward, this project can be made as complicated and difficult as you want to make it.  What I'll do here is talk about what I did to design my pattern (write a program that naively solves the generalized Firing Squad Synchronization Problem ) and some tips and tricks for doing the actual needle work on this case in particular.  The order of these steps depends on whether you are making your own design or not, but I'll try and make notes of where order explicitly does or does not matter.  I hope you enjoy my first instructable and please provide feedback on how to make it better!

Parts List
- DIY iPhone case (or from ThinkGeek)
- 3 (or more) of your favorite colors of 6-string needle-point floss
- a needle
- (recommended) some kind of thimble / finger protection
- iPhone 4, 4s or 5 (unless this is a gift)
- a 69 x 33 needle-work design
- about two weeks of hobby time
- cross-stitch design (your own or the featured one from GitHub)

In the next step, let's talk about getting the case blank design....

There are many options here, especially as you probably have many demonstrations that have been provided with the case itself.

If you are going with the cellular automaton (CA) model that I've picked, you can grab the source code on GitHub to create your own variation or recreate the original with the following MATLAB commands:

>> A = fssp(33,99,9);
>> cross_stitch(A(28:end,:));

The first command creates a matrix A that is the solution to the firing square synchronization problem.  More of this problem description is provided with the source code, but the gist is that we are trying to construct rules that will allow us to arrive at a particular state.  That is one of the interesting things about this CA problem.  Usually, we are modeling a phenomenon with the CA rules and then seeing what resulting outcome can be generated.  In this case, we are constraining the outcome and asking "What rules must exist in order to meet this constraint?"

The parameters to the command are specifying the size of the problem (to match the width of our iPhone 4 case but can be modified for other designs), for how long to "run the program" (by construction we arrive at the end of the program in 3*n steps where n is the size of the problem) and the color scheme (more on this later).

The second command creates a cropped matrix of the final steps of the program and axis plots that are appropriate for printing and using as a real cross-stitch guide.  The masking that is present is due to the rounded corners of the case, as well as the area around the camera.

Should you be using an iPhone 4 case and should you like the color scheme provided (which matches the colors of the thread that were mailed with the cases circa Fall 2011) then you don't need to do any of this!  You can simply download these designs that go on your merry way to the next step!

Should you want to tinker with the color scheme, or use this design on another sized project, there are lots of options.  I'd encourage you to play around with the 12 different color schemes that are provided in the source code fssp.m file, as well as simply using more colors.  This program--CA--finite state machine--whatever you want to call it--actually uses 16 different states / rules about those states to arrive at this answer.  That means you could use 16 colors and have them all be meaningful to the mathematics behind your design.

Also, there are solutions which require fewer states, complete in a shorter amount of time, and are also beautiful!  Experiement with everything, and let us all know what you make!

## Step 2: Do Your Cross-stitch

This happened to be my first cross stich.   Here are some tips I learned along the way:

- thimbles can be useful or get in the way.  It depend on whether you have play guitar / rock climb / have delicate fingers or not.

- you do not need to follow the instructions provided for how to do your stitches.  they recommend going bottom-left to top-right on the front, then to bottom-right on the back, and then to top-left on on the front before moving laterally to the next stitch.  This is indeed the basic stitch you'll be doing, but you'll wasted a lot of floss and you'll go very slow.  try instead:

--pulling your starting thread through back-to-front and leaving an inch or half inch to tie down.
--doing all of your bottom-right to top-left on the front stitches moving to the left along the back of the case
--moving back, left-to-right, finishing each of the stitches

This way you will tide down your thread and also power through your zig-zagging design for the long stretches across the background color.

Generally, the top-left to bottom-right (or vice-versa or vice-versa) choice will depend on which hand you use, which side of the case you start on, and what your design is doing with that color thread.  Choosing one over the other will tend to either work in your favor or against you (in terms of wasting floss or working on top of your previous work) so experiment and take note and you work through the project.

-I pulled the floss into two equal parts, but you can leave the floss with more or less strands before using it.  I imagine that 4 strands (instead of three) probably could have been ok, but it would have been tighter in places where I hadn't made the best cross-direction decision.  Feel free to experiment as the final design will thicken up or thin out depending, but I think that 2 to 3 strands would work well for this case.

-Tying off the end of a strand is as ease and threading the needle back under your work and cutting.  To do this, I could easily turn the case "instead out" so that the back was fully exposed and didn't have the lip keeping me from navigating my needle flatly along the work surface.

## Step 3: Talk (or Gift) in Style

This was a very fun project for me to develop, work on, and use.  I love the feeling of the fabric on my hands when I talk or hold my phone.  It also provided a nice, soft cushion for placing on tables or other surfaces.

I was definitely anxious about care for the case, but that soon wore off.  Color from dark pockets or just dirt and dust have faded the colors a bit, and I haven't looked into care for how to restore that.  But the case has had a good long run.  In fact, my wife is now using it on her iPhone 4 since my iPhone 5 purchase and she loves it.  It's a great gift / accessory for any geek-nerd-science-person and it's never too early to start thinking about holiday shopping.

Thanks for reading through this (my first) instructable.  I'd love any thoughts you have on the project, the accessibility of the steps and how to make this projects or its instructions better.  I consider this a living draft, so thank you in advance for your comments and I look forward to seeing all of your pretty cases.

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