Lineland
[ID: Lineland, a white line with Linelanders in it as shorter colored line segments inside of it. The Linelander on the far left is blue with both endpoints (eyes) as lighter blue, the one on the middle is light orange with darker endpoints, and the last and rightmost Linelander is pink with only one endpoint colored a darker pink. /End ID.]
Lineland. There isn't much to say beyond their singing, is there? How else could life persist? Well.. i have a few thoughts i've been thinking on Lineland and it's inhabitants. Not very complete or coherent, but fun bones to gnaw. Also some fun placeholder not-very-developed Lineland conlang words. I like using apostrophes in conlangs, sorry.
I'm allowed a bit of "its kinda magic" on some of these because, you know, 1d world.
Linelander dimorphism.
The 'females' aren't actually points. They're called points because they only have one eye (which qualifies as one point, in contrast to the 'male' that has two eyes/endpoints)
they can still look at both directions. They'll usually default to one side (the soprano to the left and the contralto to the right?) but can simply move their eye through their body
Lines are called "aauu'l" (front and behind face/two faces) and Points "aa'l" (front face/one face)
Color
Linelanders don't identify colors such as "green" "blue" etc. They instead see "front-color" (aa'ki) and "behind-color" (uu'ki)
All Linelanders are different colors but there's no way for them to know of colors beyond those that they see without trampling another Linelander or waiting for them to die to see what's beyond them and so on.
They don't see their own color even when their eyes are retracted inside of them - they can only see when their eye is exposed to air
Interactions of matter
Linelanders do eat! Where the food comes from, that's what I'm less sure of - likely the corpses of past Linelanders or other creatures of different lengths that coexist with them.
As said before, the eye of a Point can travel back and forth within the body.
Basically, an object can pass through another by swapping places with it - each cell swapping places with the other. This is easier when its a short thing trying to pass through, and also why it is pretty taboo to touch another Linelander outside of specific actions because passing through eachother is just a hassle because of said length.
Certain structures are harder to pass through (like it might take a bit longer for food to pass through the eye and then go really fast through the length of the stomach)
Linelanders always feed eachother (much like ants)
Miscellaneous things
The entire universe shrinks during their songs so that every Linelander alive is connecting with their neighbors at the same time, eye to eye (in the few seconds it takes, all Points take their eye from their front-side neighbor to their back-side neighbor), then it suddenly expands to give some constant space between all Linelanders (especially so that more can be born, even if they aren't even born near their parents)
That's why they can reproduce from so far away.
They sing by moving their eye (or eyes) through their bodies