The Textbook
One lesson to a concept, with prose that teaches it, tables worth keeping, and questions that make you use it.
The textbook is the whole course written out, from A1 to C2, covering grammar, vocabulary and the core concepts of the language, and it is free to read in full with no account and no cap. It is also what makes everything else finishable, because a correction you are given in a conversation is never only use the preterite here: it arrives with the page explaining the preterite, linked in the same breath.
How the course is organized
A course is one language, a course holds topics, and a topic holds modules, and a topic can hold other topics, so a course branches as deep as the language needs. A module is the teaching unit and the page you read, covering one concept at one level, which is a deliberately small unit and the reason you can finish one in a sitting.
What is inside one
A module opens by explaining the idea in plain language, shows it working in the target language, lays out the forms in tables you will come back to, and closes with questions that make you produce it.
Prose to read once, tables to return to
The teaching prose is worth reading once and the tables are worth returning to, which is the split to keep in mind when you are short of time. Conjugation tables, vocabulary lists and phrase banks are laid out so you can scan them later without re-reading the explanation around them, and every row carries an emoji example, so a grid of conjugations reads as fast as a picture.
What else is on the page
Inline quizzes check the concept as you go, with Show Answer and Show Hint where you need them, and Start Quiz at the top opens a longer set drawn from this module alone. Every target language word is tappable for a definition, and every sentence has a speaker button that reads it aloud.
Written for your level
Everything in a module is written for the level you are at, so the same concept at A2 and at B2 is two genuinely different pages with different examples and different expectations of you.
Why a module appears when you ask for it
Nothing in the textbook is written in advance, because a pre-written course has to guess your level and guesses wrong for almost everybody. A module is generated when you open it, pitched at where the app currently places you, which is why the first time you open one takes a moment longer than the second. The practical consequence is that the textbook has no end and no fixed order, so you cannot fall behind a syllabus being written for you as you go, and you can ask for a module on something the course never covered, which is one of the allowances in Generating Your Own Content.
Finding your way around
The Textbook page for a course opens with the modules you were last working on, then the full topic tree underneath, and the tree collapses by branch so you can fold away the parts you are not using. Next Up, Stacked and Random reorder the modules at the top, and Next Up follows your study plan.
Getting the most out of one
Read the module once without stopping, then answer the questions before going back to the tables, because checking the answer as you go turns language production back into recognition. When you get one wrong, read the explanation and not the correct answer, because the answer teaches you one sentence and the explanation teaches you the pattern.
What to do next
Work across different modules and avoid repeating a single one, because Your Level counts breadth far more heavily than repetition. When a module stops being difficult, take the same material into a voice scenario and try to say it out loud under time pressure, because that is usually where you discover that knowing it and being able to use it are two different things.
When a module counts as done
A module is completed once you have enough questions right on it, and finished outright once every question on it is right, and each of those first transitions pays gems once.
Limits
The textbook itself has no cap on any tier. Questions inside a module are capped for a visitor with no account, at a handful per module, a free account raises that to a hundred per module, and Pro removes it.