what happens between your finger and the light?

image: ai-generated (gpt-image-2)

behind the switch

the switch is the whole contract: up, down.

so here is the word for it

an abstraction hides how something works
and shows what you can do with it.

the part it shows you is called the interface.

three you used today without noticing

from a photo to light, one layer at a time

each layer talks only to the one
directly below it.

that single rule is what makes everything else possible.

what that buys you

not tidiness. this is why one can change without the other.

which of these may talk to the led?

same stack, different bottom

five layers unchanged. one exchanged.

you extend your alphabet from four colours to eight

a frame is defined in bits, not in colours

and it says nothing about time.

time belongs to the path, not to the message. that is why sound works.

everything here sits on light.

light is the layer you could replace.

layers are not free

wrong letters arrive. where do you look first?

a tested layer is a layer you can stop suspecting.

how to test one layer

feed it a known input, check its output,
with nothing below it.

bits in, bits out. no led, no sensor, no room light.

why doesn't it hide everything?

a good interface hides what you don't need and shows what you must decide.

you know what's under the switch.
every layer you write is one.

image: ai-generated (gpt-image-2)