One problem is that syntax is just one (rather shallow) part of the design of a programming language, but it's one that gets a lot of attention because everyone who's used two programming languages can tell that it's a point where languages differ. Semantics (rules about what blobs of syntax mean) is a much more interesting way for languages to differ, but most "build a language" tutorials I (and probably GP) have seen don't seem aware that there are even decisions to be made there. The "your own" bit in the title is also a bit upsetting for a post that hands the reader a language and its implementation instead of talking about something of the reader's own design.