The recent Cuneiforth experience reminded me of Carl Sagan’s Contact, which I read soon after leaving high school. It describes how an alien civilization establishes communication with us over a radio link 26 light years long. The repeating message consists of a long sequence of binary encoded over radio somehow that I don’t recall, with the first few frames consisting of long sequences of all 0s and all 1s. The numbers of 0s and 1s is equal, and the product of two prime numbers, which suggests rasterizing them as pixels. (Interestingly, now I think of it I believe you can do this in any combination of two directions, and the rest of the sequence continues to work.) After a few frames of this they start writing out sequences and attaching symbols to them. This is 1, this is 2, this is 3. Then later pages start saying things like 1+1 = 2, etc. establishing the symbols for ‘+’, ‘=’ and so on in a very gradual way with lots of redundancy to catch decoding errors quickly. And of course, since this is fiction, the instructions culminate in teaching humanity to build a whole new tech they’ve never seen before.
A hazy thought I’ve had: it might be fun to build something like this as a game for my kids 
Very different definition of bootstrapping from this thread, but maybe interesting to think about.