How this is built
First principles, as a reading interface.
Most explanations start in the middle of a field: they use the field's words, then tell you the conclusion. Primer starts at the bottom — the facts that would still be true if the field had no name — and only then walks up.
What a first principle is
A first principle is a claim you are not allowed to rest on a more basic claim in this discussion. “Air is made of molecules that can push” is a first principle for flight. “Wings produce lift because of Bernoulli” is not: it names an effect without saying what the air is doing, and it uses a word the reader may not have.
The test is practical. If you deleted the vocabulary of the subject, could you still point at the stuff, the push, and the constraint? If not, you have not gone deep enough.
The stack Primer uses
00 Bedrock
What exists. Matter, force, energy, incentive, a rule of logic. Named in ordinary language.
01 Cause
How those primitives interact. Forces come in pairs. Tension is a pull. Short waves scatter more.
02 Mechanism
The specific arrangement that uses the cause: a wing throwing air down, steel sitting in a stretching face, air peeling blue out of sunlight.
03 Practice
What to look for, derived from the mechanism, not copied from a checklist you are asked to trust.
Every word, once
A technical word is a compressed explanation. If you meet it before the explanation, it is a locked door. Primer defines each such word in plain language the first time it is used, marks it in the text, and collects the definitions at the end so the page is also a glossary.
Analogies are labeled as analogies. They come after the real cause. A hammock is not how rebar works; it is a picture of tension versus compression after that distinction has already been made.
Pictures that argue
Three kinds, and none of them is decoration. A photograph puts you in front of the phenomenon. A typed diagram (forces, stacks, flows) states a structure. A graph is for when the cause is a relationship: as tilt grows, lift rises then falls; as wavelength grows, scatter collapses. If a picture would not add a cause, it is omitted.
What actually improves learning
Most “learning features” are engagement dressed as pedagogy: streaks, points, a warmer chatbot. They make you come back. They do not make the mechanism stick. The findings that do:
Retrieval, not rereading
Trying to answer from memory, even badly, beats highlighting. That is why a primer ends in “Close the book” — questions that need the mechanism, uncovered only after you attempt them. There is no score. A score would train you to hunt the phrase, not the cause.
Elicit your model, then correct that sentence
Naming a misconception as a general phenomenon (“a common mistake is…”) installs a labeled wrong model and burns the bait. Primer asks you to commit first: where the weight goes, what the shaft does, what still looks correct. Then it replaces your sentence. If you skip the checkpoint, the lecture does not stall — it teaches on.
Make the model forecast a reading
Refutation that only says “no” does not stick. Once you have committed, the primer asks what your model would have to produce — a gauge, a sound, a failure — then shows the observation you actually get. A model that cannot predict has nowhere to hide.
Say it without the page
One sentence in your words. If you cannot name the stuff, the push, and the constraint, you have the field's costume, not the mechanism. Comparing to the primer's sentence is the test — not an AI grade.
See how X moves Y
A paragraph that says “scatter falls with the fourth power of wavelength” is easy to nod at. A curve that drops from violet to red is harder to fake. Graphs here are schematic on purpose: the shape is the argument, not a pretense of lab precision.
Take the mechanism somewhere new
Recalling the airplane is not the same as having lift. A paper plane, a balcony instead of a beam, the Moon instead of Earth — if the cause still names itself, you have it. If you only have the example, you have a story.
Generate the next because
“Why does this follow?” asks you first. Extra explanation from Primer is available after that attempt. Reading another paragraph is easier. It is also how slogans survive.
Close on the record that proves it
For plant work the unit of mastery is not “can do.” It is “can tell whether it was done, from a record.” Where it lives, the silent install error, the paper that catches it, the failure signature if nobody looked. Primer will not invent a document number, a setpoint, or a torque as if it came from a drawing. Where the fact depends on this plant’s vendor or permit, Primer names the kind of paper — one-line, P&ID, submittal — and stops.
What we are not adding: points, leagues, daily goals, a mastery percent, a tutor that withholds the next paragraph until you answer, grades, or a spaced-repetition calendar. Those belong to an exam product. Primer is the reading surface — purpose, law, worked instance, then vocabulary. Checkpoints never gate it.
This plant
The intended reader is a construction project engineer on an islanded, behind-the-meter, simple-cycle gas-turbine plant serving a computing load. Not the designer. Someone who has to catch a bad drawing, write an RFI that does not donate the stamp, and be useful at first fire.
Islanded, behind-the-meter, and off-grid are three different facts. Frequency on an island is shaft speed from power imbalance, not a setpoint someone “holds.” Generator fault current decays — that is why a plain 51 can stare at a fault and never pick up. Black start is the only start. Nameplate is not site rating and not net to the customer. A primer that invents this plant’s megawatts, kV, or ammonia percent is worse than one that says go look at the one-line.
The plant catalog is the topic map. The unverified list on that page is not filler — it is the list of things Primer is forbidden to guess.
How to use it
Ask a real question. Read from layer zero, even if you think you already know the ending — the ending is usually the part that was memorized. Tap a marked word. If a principle still feels like a slogan, press “Why does this follow?” — try the because yourself, then add a layer if a step is still missing.
When you reach the end: walk the because-map, commit at the checkpoints, close the book, take the mechanism somewhere new, say it in one sentence. For this plant, start from the plant catalog or the trades list. Save the ones you want to keep.