Because

1. When the internet was rolling out, a decentralized, open, best-effort solution of TCP/IP thankfully won over telephone companies’ centralized system proposal
2. IPv6 is still not universal for some damn reason
3. Onion addresses solve these problems but good luck getting everyone aboard with Tor
4. You always trade anonymity for reachability, and with the amount of threats, NAT and firewalls have been put up to make it harder for unsolicited requests to reach you by default

Don’t go into Seine, you’ll drown!

(I know it’s pronounced [ˈzaɪ̯nə] 🔊, I can speak German)

Yeah, it’s fun but the temperature needs to be correct. With rising temperature, the paper goes black, light gray, brown and then glowing orange.

I am not aware of any receipt printers using lasers - thermal printers have an array of resistors that get hot when necessary. I know how a laser printer works and it is hard to explain in 12 or so words. Inkjets are way easier, you can just say “squirt squirt oops”. Anyway…

1. A photosensitive drum gets a negative electrostatic charge.
2. A laser shining through a rotating prism scans lines across the drum’s surface. This removes charge from parts of the drum that should not be covered in toner.
3. A high-voltage corona wire inside the toner reservoir charges an amount of toner positively.
4. The charged drum rotates past the corona wire, getting covered in toner where its negative charge remains.
5. Paper is pushed against the drum and the powdery toner is transferred to it.
6. The paper continues into a fuser, a little oven where a heating element briefly makes the toner so hot that it melts, its powder particles making a permanent bond among themselves and with the paper. (The heater is usually stationary and heats the paper from below. The fuser drum that pushes paper against the heater can get sticky and pick up some of the toner, making images repeat down the page. This is the most common failure mode that cannot be resolved through regular maintenance such as replacing the toner cartridge and printing cleaning pages. However, almost all laser printers have a cheap fuser module or its drum available so it is usually worth replacing.)

Time travel is a prerequisite but don’t worry, you can just

from __future__ import antigravity

Laser printers more accurately “bake paper so that number powder sticks to it”