Riemann Labs

Leo won’t do your homework. He makes sure you can.

Leo is an AI tutor. Tell him what you’re learning: he plans the days up to your exam, teaches one idea at a time and asks for your attempt before he shows you his.

Free to start, no card needed. Your first week has all of Leo. After it he stays free, a few hours a week.

Or bring one problem and try it now, without an account

The research

Let an AI think for you, and less of it stays with you.

When an AI hands you the answer, the work looks better and you remember less of it. When it makes you do the thinking, you learn more. Three studies, one pattern.

AI use reduces brain activity

Couldn’t correctly quote the essay they had just written

with ChatGPT83%couldn’t correctly quote their own essay, written with ChatGPT
on their own11%couldn’t correctly quote their own essay, written without ChatGPT

Minutes after handing in, 15 of 18 people who wrote with ChatGPT couldn’t quote their own essay. Writing alone, it was 2 of 18.

Kosmyna et al., 2025 · 54 adults, a preprint not yet peer-reviewed

About this study

54 people from universities around Boston wrote essays on their own, with a search engine or with ChatGPT, while an EEG cap recorded their brain activity. In the ChatGPT group the researchers measured the weakest connections between brain regions, and right after handing in, 15 of 18 couldn’t correctly quote what they had just written. In each of the other two groups it was 2 of 18.

Students with ordinary chatbots do worse

Grades, compared with students who never had the chatbot

in the exam, without it−17%exam grades, once it was taken away
while practising with it+48%practice grades, with a chatbot that gives answers

Better while the chatbot was there, worse once it was gone. A tutor that gave hints instead of answers showed no such drop.

Bastani et al., 2025 · nearly 1,000 high-school students

About this study

Students who practised maths with a standard chatbot did far better while they had it, and 17% worse in the exam without it. A tutor set up to give hints instead of answers removed that drop. How an AI helps decides whether it helps.

An AI tutor built on teaching research can radically improve real learning outcomes

Median learning gain on the same material

with the AI tutorover 2×learning gain with the AI tutor, in less time
active-learning class1×learning gain in an active-learning class

Same students, same course: with a tutor built to make them think, the median learning gain more than doubled, in less time.

Kestin et al., 2025 · 194 students

About this study

In a randomised trial in Harvard’s introductory physics course, each student learned one topic from an AI tutor designed around teaching research and another in a well-run active-learning class. With the tutor, the median learning gain was more than double, and it took them less time.

So Leo asks for your attempt before he shows you his and gives a hint where a chatbot gives the answer. The thinking stays yours.

These studies tested ChatGPT and other AI tutors, not Leo. We have not yet tested Leo himself.

How it works

Everything a tutor does, in one conversation.

You talk to Leo. What he makes shows up right there, and stays yours.

Conversation

He remembers what you learned, and where you slip.

Leo brings back what you learned before it fades, asks for your attempt before he shows you his, and notices when the same mistake comes back.

Analysis I · lesson 7 of 14THU 18:05

Before Taylor series: the chain rule was nine days ago. Quick one, what is the derivative of e³ˣ?

He brings it backNine days on, just before it fades.

3·e³ˣ

Right. Now 3(b) from your sheet, ∫ x·eˣ dx. Your attempt first.

Your attempt firstThe worked solution comes after a real try.

x·eˣ + ∫ eˣ dx = x·eˣ + eˣ + C

The set-up is right. Look at the sign before the integral: that’s the third time this week, so it’s on Saturday’s plan.

He sees the patternA slip that keeps coming back becomes a weak spot, with time for it in the plan.

Flashcards

Cards that come back before you forget.

Leo drafts cards from what you learned and you keep the good ones. Each comes back when it is about to fade.

Card 3 of 12 due today

What does the chain rule say?

Quick checks

One question, and the mistake behind a wrong answer.

After each idea Leo checks it with a question. A wrong answer gets what it usually means, not just a red cross. Try it.

Quick check

What is the derivative of sin(x²)?

Goals

Tell him the date. He plans the days.

Give Leo a goal and a deadline and he lays out the lessons up to it, around the days you study, and tells you how ready you are.

Your goal

Pass Analysis I

Exam in 12 days

Ready64%
  • TodayTaylor series25 min
  • ThuMock exam60 min
  • SatSigns in integration by parts15 min

Interactive widgets

Ideas you can take in your hands.

When an idea has something to move, Leo builds a widget for it, in any subject. Here are two: who really pays a tax, and how pure tones add up to any wave.

The law says sellers pay the tax. Who really pays it?

  • Buyers pay 78%
  • Sellers pay 22%
  • Trade lost 8 of 50 units
€20
a little
a lot
Handed to the state by

The law makes the sellers hand over €20 a unit. Buyers now pay €65.5 (was €50), sellers keep €45.5. Buyers react less to price, so they carry most of it, whoever the law charges.

Technology

A system, not a chat window.

Around the language model, Leo’s app plans your lessons, has you try before you see a solution, keeps track of what you know, and comes back to your mistakes.

See how it works inside
  1. A study planPlanned backwards from your exam date. Miss a day and the lessons move on; nothing turns overdue.
  2. Try firstLeo shows the full solution only after you have tried the problem yourself.
  3. A memoryLeo keeps track of what you know and what you are forgetting.
  4. RepetitionLeo remembers your mistakes and brings those topics back on his own.

Free to start. Free to stay.

Your first week has all of Leo, with no card. After it you stay on Free, or pick a plan for more.

Free

Leo, every week, at no cost.

€0

no card, no end date

  • First week: everything, the knowledge map included
  • A few hours with Leo every week
  • Up to 3 goals at a time
  • 5 materials in your library
  • Your cards, always
Get startedNo card needed

Student

A tutor for what you are working on now.

€12.99a month

No VAT is charged under § 19 UStG.

  • Your knowledge: the map of what you know and the notebook Leo writes
  • Enough for two hours with Leo every day
  • Up to 5 goals at a time
  • Mock exams in the style of your past papers
  • 15 materials and 5 hours of lecture recordings

Master

For long study days and a big library.

€21.99a month

No VAT is charged under § 19 UStG.

  • Everything in Student
  • Room for long study days, every day
  • Up to 10 goals at a time
  • 30 materials and 15 hours of lecture recordings

Prices in euros, billed monthly. Change or cancel any time. Every account starts with a week of everything, no card needed, and stays free afterwards with a few hours of Leo a week.

What you make is yours. Your cards leave as a file Anki or a spreadsheet reads, your notes as Markdown files, whenever you like and without a plan.

Questions before you start

Straight answers. If yours isn’t here, ask Leo.

What does Leo cost?

Nothing to start, and nothing to stay. Your first 7 days have the whole of Leo, and starting needs no card. After them you stay on Free, at no cost, unless you choose a plan: Student at €12.99 a month or Master at €21.99. On Free Leo keeps teaching you for a few hours every week, with up to 3 goals and 5 materials, and your cards keep working as before. What a plan adds is Your knowledge (the map of what you know and the notebook Leo writes, which he keeps for you meanwhile), more time, more goals and a bigger library. Whatever you choose, your cards and notes can be exported at any time.

How is Leo different from ChatGPT or Gemini?

ChatGPT and Gemini are general assistants that help with almost anything, and both have study features you can open when you want them. Leo only tutors. He keeps a plan for each of your goals and knows what today needs, asks for your attempt before he shows a solution, brings back what you are about to forget, and keeps one notebook and one map of what you know across every subject. He also notices what keeps tripping you up, and checks it again before your exam.

Is there a limit to how much I can study?

Each plan holds an amount of time with Leo for the month: Student is enough for two hours every day, Master has room for long study days. Your plan page shows how much of the month is used, in plain words. You are told when four fifths are used, and if a month does run out you can add more for €5 instead of changing your plan. Reviewing cards, reading notes and your library never count.

Will Leo just give me the answers?

No. He explains a new idea as fully as it needs. A problem you bring starts with your own attempt: he asks for a first step, makes the step smaller when you are stuck, and shows the worked solution after a real try. Send a photo of your working and he finds the first line that goes wrong.

How do I know what Leo tells me is right?

Answers with a number are checked by the app, not by the AI. When Leo reads your own material he shows the page he read. A specific he cannot verify, such as a quotation, an exact figure or what your exam board requires, carries a "check this" mark. And "This is wrong" under any reply or grade reaches the people who make Leo. He is an AI and can be wrong: for anything your grade depends on, your course's own materials are the authority.

Can I bring my cards from Quizlet or Anki, and take them with me?

Yes, both ways. Paste a Quizlet export, a spreadsheet's CSV or an Anki text export into a conversation and Leo makes a deck of it. Your cards leave as a CSV file or as a file Anki imports, and your notes as Markdown files, whenever you like, with or without a plan.

Which subjects and levels?

Whatever you are working toward, said in one sentence: an exam with a date, a course at school or university, a skill, a project. Leo lays out a course for it from what he knows and builds on your own materials when you add them: a syllabus, lecture slides, a chapter, past papers. Mock exams follow the style of the past papers you bring.

Which languages?

The app is in English and in German. Leo answers in the language you write to him, whichever it is, and you can set the language he teaches in.

Who is Leo for?

Learners from 17: school-leaving exams, university courses, professional exams, a language, anything you are working toward. You give your month and year of birth when you sign up. Paid plans are from 18.

What happens to what I write and upload?

Your account, conversations, notes and uploads are stored on servers in Germany. To write each reply, Leo sends what you write, the files you share and what he knows about your goals to OpenAI, whose models he runs on; it is not used to train AI models. You can download everything or delete your account at any time in Settings. The privacy policy, linked at the bottom of every page, has the details.

What do I need to use it?

A current browser. Leo is built for a laptop or desktop and also works in the browser of a phone or a tablet. There is nothing to install.