Guide
You can learn almost anything in an afternoon.
A week later, most of it is gone.
That is not a flaw in you. It is how memory works.
That is the first thing the app says to a new learner, and it is the reason the app exists. Everything below is about the second half: bringing each idea back just before you would forget it.
The tutor
The tutor is an AI. It designs the curriculum for each topic you create and teaches it to you in conversation. A separate grader, also an AI, marks what you write; the Learn section says how. What the tutor does not do is decide when you see something again: review dates come from a fixed scheduling algorithm working on your own results, and the tutor never touches them. What you write to the tutor is sent to the AI provider to generate its replies; the privacy policy says who that is and what is kept.
Signing in
The only way in is Sign in with Apple. There is no password and nothing to remember. You can use Apple's Hide My Email; the app does not need your real address.
Due
The home screen. It lists what is due for review right now, across every topic, in the order the scheduler wants it. An empty Due screen is a good sign: nothing needs you yet. Tap an item to review it.
Topics
A topic is a subject you want to learn, in your own words: “the French Revolution”, “how TCP congestion control works”, “understand the basics of photosynthesis”. Creating one asks the tutor to design a curriculum, a set of connected nodes from foundations to the hard parts, and that takes about a minute. Open a topic to see its nodes and start learning.
Learn
A learn session is a conversation with the tutor about one node. The tutor explains the idea, but before each step it asks what you think will happen. At the end it asks you to explain the idea back in your own words. Commit to an answer before the tutor reveals anything; even a guess helps ensure the answer is retained.
Your explanation is graded blind. The grader is a second AI, separate from the tutor, and it is given only two things: what you wrote, and the standard it is held to. It never sees the conversation, so it cannot be swayed by how the lesson went or by anything the tutor said. The grade, and the review intervals the scheduler chooses from it, are computed by the app's engine, never by the tutor or the grader.
Review
A review session re-tests a node you already learned. Answer from memory first. The scheduler uses how well you did to set the next review date, so a hard recall brings the node back sooner and an easy one pushes it further out.
Explorable
Some nodes can be turned into an explorable, a small interactive page built for that node once you have learned it. Open a node inside a topic to see whether one is available.
Flashcards
Flashcards is the one part of Know It Cold that is not a tutored topic, and it is always in your topic list. It holds two-sided items you add yourself on its Entries screen: a word and its definition, a date and its event, an acronym and its expansion, a formula and its name. There is no curriculum and no conversation. Adding an item starts its schedule as if you had just learned it. When it comes due, the Review screen shows one side, asks you to type the other from memory, grades what you typed against what you stored, and moves on to the next card.
The rule of thumb for which to use: if the thing has a why to it, something that can be explained and misunderstood, make it a topic and let the tutor teach it. If it is a bare pairing you already understand and only need to keep, put it in Flashcards. “How photosynthesis works” is a topic; “stoma: a pore in a leaf that lets gases in and out” is a flashcard.
Settings
The Settings screen has four sections. Account shows which account you are signed in with and lets you sign out. Explorables chooses whether explorables are built for visual ideas as you go, or only when you ask for one. Data lets you erase the copies of your conversations kept on the phone and any error reports waiting to be sent. About prints the version, commit and server address the app is using, links to this guide, the privacy policy and the support page, and opens Licenses, the open-source notices the app ships with. If you report a problem, the About rows are the first thing to send us; the support page says which.