it's a nice art in general but the lines are often not perfectly 2:1 diagonal, which makes them look bumpy and uneven, commonly known as jaggies
here's my attempt at cleaning it up (i hereby place my modifications under cc0), i'm not sure what to do about the inner walls of the ceiling though (could just drop the lower lines down a pixel but i'm not super sure about that)
here's a text-to-speech engine with a bunch of voices under various cc licenses, some foss-compatible: https://github.com/rhasspy/piper
(though most of them were trained by starting from the model for "lessac", which has a restrictive research license; idk how much that matters though)
and here's an asset pack made with it: https://rancidbacon.itch.io/dialogue-tool-for-larynx-text-to-speech
another format i've seen in use is a single grayscale image, where each pixel's brightness determines at what point it switches to the second image
it's natively supported in ren'py and it seems to be used somewhat widely outside of it too (godot tutorial, game maker shader, rpg maker plugin, compatible generator)
it's a nice art in general but the lines are often not perfectly 2:1 diagonal, which makes them look bumpy and uneven, commonly known as jaggies
here's my attempt at cleaning it up (i hereby place my modifications under cc0), i'm not sure what to do about the inner walls of the ceiling though (could just drop the lower lines down a pixel but i'm not super sure about that)