Way to steal my karma.... :)<p>As the original author of this, I was going to put it into a much more presentable state before showing it off here.<p>For those confused, here's a proper explanation. No real-world thing can actually be Turing complete (able to express basically any computation that we might want to perform of any size). That's because there are finitely many atoms in the universe, so we can only construct machines of finite size.<p>It's well known that Rule 110 (Google it) is Turing Compete.<p>What I've done is made an implementation of Rule 110 in HTML and CSS. Since CSS can't actually really manipulate state, some user interaction is required to "drive" it. In the one that bgruber linked to, it's clicking.<p>Here's a bigger version that doesn't require the user to know where to put his mouse. The tab-space combo is just as legitimate as requiring that you plug a computer into a wall to power it in order to run a Java program. <a href="http://elilies.com/rule110-full.html" rel="nofollow">http://elilies.com/rule110-full.html</a><p>Also, I haven't tested it on anything besides the latest Chrome on Mac.
I'd like a more complete description of this.<p>My first thought is "no it's not", because you are encoding a fixed-sized grid in the HTML, which is then the total extent of the program. While no real machine has an "infinite tape", I think requiring the tape be embedded in the program itself is strengthing things a little far.
There are two competing definitions of Turing complete here.<p>1. The mathematical definition of Turing completeness: models which can simulate the computation of a hypothetical Turing machine. Idealized circuits are an example of this. Turing machines are an example of this. Programs with infinite memory are an example of this.<p>2. The colloquial definition of Turing completeness: this is naturally ill-defined, but it roughly means an automated, finite model that performs arbitrary computation. I would say that a robotic Lego Turing machine is Turing complete. C is certainly Turing complete in this sense. Basic HTML isn't. The set of regexes (e.g, unix wildcards) isn't.<p>However, if I can choose a large enough regex, I can construct a decider for a given finite language. How then are regexes less powerful than C? The answer is they are just as powerful in the finite case, unless we set reasonable limits on what we mean by 'finite' and 'automated.'<p>This HTML+CSS is not Turing complete. The idealized version of this HTML+CSS is not Turing complete (unless you strangely accept the idealization of a "hand pressing tab space"). This HTML+CSS is also not Turing complete in the colloquial sense: it doesn't live up to the generally accepted notion of automation. It isn't executed by the machine.
As far as I remember is LaTeX (or TeX itself) touring complete, too. In the end, if you can simulate a turing machine (or another "equivalent" calculating "device") the language is itself turing complete. While not being a html/css wizard, by the amount of complex examples i saw you could do with only HTML/CSS3, I am not surprised that you can write a cellular automaton in it.<p>edit: typo (personal hangup with touring/turing)