Wearable Muscles

A lot of the typical difference between the male and female upper body comes down to this specialization. There is some evidence of facial adjustment to punching, but we could hit much harder with a more chimp-like shoulder, this doesn't require knuckle walking: but we wouldn't throw a spear as far nor as accurately.

This ensures that your eyes/brain can easily distinct between two lines and "hop" along. The upper limit ensures that you won't lose track of the line because two lines are too far away from each other.

Line length limit comes from this, too. It's hard work for the brain to save a line you just read, jump back to the start of the next line and continue. Short (but not too short!) lines help with that, too.

Paragraph margins are historically based on blank lines, so you can adapt that for your digital text, too and use margin-bottom: 1em or sth. like that (better use the line-height value for the margi, so you include that space, too).

Rules like these obviously date back to the print age, as there are several types of reading (more technical "ways to obtain the information") defined and refered to in "design rules".

You'll "read" a large poster different than a dictionary which is why you can/should deviate from these rules, depending on the setting.

Headlines for example don't need a line-height of 160% but will often work very well with 120% or even smaller. There are no strict rules but more guidelines, so you'll have to develop a sense and feel for that.

Other design rules and their implications play a role, too. Contrast of text to background, phenomena of large color areas, stroke-width of the font and lots of more.

For web typo with I am personally using sans-serif fonts with a larger font-size. Even with wider layouts this helps with getting shorter lines, slightly larger typo improves readability, more line-height reduces the "wall of text" effect, paragraph margins help to distinct different parts of text from each other.

There should be good beginners literature available if you find this interesting.

Also: Try fiddling with the etzh.ch page. Set the line-height to 1.2 and the font-size to 1 rem and you'll immediately see how not to do it. :-D

0: https://en.m.wikipedia.org/wiki/Pteranodon

  The bodies of flying creatures are not so materially lighter than those of other animals, as to justify us in considering this difference in weight an essential condition of flight. It is often asserted that the hollow bones of birds facilitate their flight, especially since the hollows are filled with heated air, but it does not require much thought to come to the conclusion that this diminution of weight is barely worth mentioning. Also, we have not been able as yet to prove that the muscle and bone substance, as well as other parts of the bird's body, are specifically light. [...] After a bird is plucked, no one will assert that it is propor­ tionally lighter than other animals, and our housewives are certainly not under the impression that a pound of bird's flesh, even with the hollow bone included, is more bulky than an equal weight of flesh from another animal. [0]

I do have to say, whenever I see a stork above, or even just a red kite or pelican, I feel envious. Our drones and planes just seem crude in comparison.

To be clear: I'm not talking about flight as a means to get from A to B as quickly as possible. That's the domain of the jet engine, and no bird can match it. I'm talking about flying as a thing you do for the enjoyment of it, as a thing of beauty and wonder. In short, that which inspired humans to dream about flying machines in the first place.

Basically the only thing missing is the functionality for paraglide to become rigid structure on demand and they will be bombproof. There is some initial progress in this regard but its a long way from reality. Endgame would be probably some electrically-induced rigidity via some easy-to-manage remote. Or some smart behavior in between based on whats happening, that would allow easily things not considered possible currently.

To fly like a bird, you probably need more motion control over the wings than just "up and down". I believe birds can angle their wings, they can curve them, and they can sense differences in air speed and air pressure across the wing's surface. That's why it seems to me that any form of artificial muscle would be a huge step.