LanterninaAn afternoon on paper, invented for one person and approved by a parent
Language: English

A project built in one house. The code, the measurements and the open problems are public.

Source on GitHub ↗

Three diagrams

How it flows

Who is allowed to ask whom, what happens to an afternoon between being invented and being over, and what a sheet of paper does on its round trip.

1. Who asks whom

Every arrow that crosses into the house is the answer to a request the house made. There is no inbound path: the panel writes a row, and the hub finds it the next time it asks. That is what makes the dashboard inert — changing a setting stores a new state and makes nothing happen in a room.

Who asks whomThe house holds a hub, two e-paper displays, a button, a printer and a scanner. The hub sends one arrow out to the panel and API in Azure, and the panel answers inside the reply. Inside Azure the panel passes work to the model router, the router to Content Safety, and Content Safety to Microsoft Foundry. A parent in a browser writes a row to the panel. No arrow starts in Azure and ends in the house.The houseAzure, EU regionA parent, in a browserapproves, and sets the hourswrites a rowe-paper displaysa finished 1-bit bitmapa buttonanswered in the replyHubclock · sealing keys · print queuethe only thing that starts workprinter · scannerone A4 sheet at a timeshowsa pressout, and back inpanel + APIholds decisions, starts nothingmodel routerthe only module allowed a model SDKContent Safetymints the screened payloadMicrosoft Foundrylanguage · vision · imageasks,on its own clockanswers,inside the reply
Both edges across the middle begin on the left. A parent's approval enters at the top right and stops there: it is a row, not an instruction.

No model runs on the device, and an import-level test refuses an on-device runtime in every package including the router. The trade is stated plainly: one inference path instead of two, no weights to ship — at the price that a page which comes back while the cloud is unreachable stays unread until it is reachable.

2. The life of an afternoon

One document, written in a single pass before anybody has read a word of it. It holds every moment, three lengths of each, a four-rung ladder of help under each, and a way out. Nothing is added while it runs — which is what lets the same moment be shortened, or put on a display that holds forty words, and still reach the same ending.

The life of an afternoonThe house asks for an idea. A model writes the whole afternoon in one pass. Six checks and a second model reread it, and a refusal sends it back to be written again. It then waits for a parent, who approves. The house begins it. A moment runs, and what came back either starts the next moment, or is sent up as an ask which returns a continuation, or closes the afternoon on its object.The house asks for an ideait keeps a few readyA model writes the whole afternoonevery moment at once — 68–157 sSix checks, then a second modelrereads the whole thing — 14.4–22.8 sIt waits for a parentnothing prints, nothing wakesThe house begins itonly if the whole length still fitsA moment runssay · hand over · collectWhat came backmarks, or blankIt ends on the objectthe same ending, however it wentaskthe house sends up the blank and thepage that came back, and receives acontinuation in the same formatpassesapproving writes a rowit closesrefusedthe next momentaska continuation, in the same format
The two edges that turn back are where the cost is. A refusal on the left buys another whole devise; an ask on the right is the afternoon admitting it is not finished being written.

Two edges are worth reading twice. A refusal costs a whole new devise, which is why a check that reads a phrasing instead of a fact is expensive: one such check was the most frequent refusal until it was fixed. And an afternoon begins only if its whole length still fits before the hour the parent set — thirty minutes before that hour the way out starts, whatever has been reached, and no display says it was shortened.

3. The paper round trip

The part with the least machinery in it. Nothing is printed on the paper for a machine to find, so there is nothing to detect, rectify or decode.

The paper round tripWords that have already passed the safety gate go into one image call, which draws the whole sheet. The sheet is printed and its blank is kept. Somebody writes on it, or does not. The scanner takes it back, both images go to a model, and the answer is either marks or blank. That answer is what the next words are written from.Wordsalready through the safety gateOne image callthe whole A4 sheet, in one pass19–33 sPrintedthe blank is kept: it is what thereading is compared againstSomebody writes on itor does notScanner≈ 26 sTwo images to a modelwhat is different? — 4.4–5.5 smarks · blankthe whole vocabulary,then the reading is goneand the next words are written from it
One box in the ring is not machinery, and nothing in the system can make it happen.

The reading is gone in the strong sense: not written to storage, not to a log, not anywhere a person could read it later. Not a count and not a fraction either, because a count of somebody's marks is one step from a score.

Measured with a finger on a real button: press to reading on the display, about 35 s, of which 26 s is the scanner. The floor is the scanner plus up to one wake cycle of the display, and the firmware adds 5–11 s to any refresh interval you ask for.

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