Everything below is a real lesson block, running the same code your lessons will. Tell Leitner what you want to learn and it builds a course out of these, then brings the ideas back before you forget them.
Friction on a slope. Change the angle or µ while it's moving — the block keeps whatever speed it already had.
Gravity down the slope beats friction, so the block accelerates at a constant 1.40 m/s². That's why speed climbs in a straight line while distance curves upward — distance is the area under the speed graph. Mass never appears in either sum.
Start with nothing in the box.
Blue is blood that has given up its oxygen, red is blood that has just collected some. Click any stage to read what happens there.
The vertex sits at x = −b/2a, which is why it slides sideways when you move b alone. The sign of a decides which way the curve opens, and its size decides how tight it is.
From year 22 the interest is doing more of the work than you are: everything above the green line is money the account made on its own. Over 25 years you pay in $60k and it earns $79k.
Adoption spreads through five groups, and each needs a different kind of evidence before it moves — which is why one message never reaches all of them. Pick a segment to read what it takes.
An exam in three weeks, a language you keep abandoning, a reading list. Describe it in your own words — it asks questions back until the plan is one you would actually follow.
A syllabus, lecture notes, a textbook chapter. It reads them and builds around your course structure rather than a generic one. Your files stay yours and are never pooled with anyone else’s.
Each lesson is something you do rather than read. Whatever you get wrong comes back a few days later, and again after that, until it stops coming back.
The mechanics are the same whatever the subject — a slider is a slider whether it is moving a coefficient or a rate of return. What changes is what it is a slider for.
The blocks above are the answer to that. A lesson is something you interact with — a simulation to push, a trace to step through, a diagram to take apart — and the model’s job is to build those and mark what you do with them, not to talk at you. There is a chat inside every lesson, but it is for asking about the thing in front of you.
It is read to build your plan and then it stays yours. Your files are never added to a shared library, never used to build anybody else’s course, and never used as training data. You can export everything the account holds, or delete the account and take it all with it.
Whatever you get wrong comes back — a few days later, then again after a longer gap, and it keeps stretching as long as you keep getting it right. That is the Leitner system, and it is where the name comes from. What comes back is the specific idea you missed, not the whole lesson.
Yes, and the first lesson of every plan is free before you decide anything. Single lessons are priced by length, minutes you buy never expire, and buying the rest of a plan at once costs less per minute than buying them one at a time.
Still have questions? Write to us — you do not need an account.
The first lesson of every plan, on the house. Draft up to 3 plans and see exactly how a topic is taught before you pay for anything.
Start herePriced by length — $0.50 plus $0.06 a minute, and less per minute if you buy the rest of a plan at once. No subscription, and reviews keep running on everything you own.
See a plan first10 hours of lessons a week across up to 10 plans, every lesson type, and full review scheduling. The right size if you are learning one thing properly.
Go minimal30 hours of lessons a week across up to 20 plans, and the most room to ask questions inside a lesson. For several subjects at once, or one taken seriously.
Go maxMinutes you buy do not expire and work on any plan. A subscription is what to take when buying lessons one at a time stops being the cheaper way round.