Try a real deck
These cards come from a real book. Flip one, grade how well you knew it, and see when the deck brings it back.
Loading the demo world…
Space to flip, 1–4 to grade.Tap the card to flip it, then tap a grade. Your progress moves to your account when you sign up.
How a PDF becomes a deck
Upload once; the cards are written and scheduled for you.
Upload the PDF
Lecture notes, a textbook, slides saved as PDF, a manual: any PDF or EPUB up to 50 MB, in any language. A scan needs a text layer.
The key ideas become cards
The document is read for its key ideas, each becoming up to three questions. The question is the front of the card; the answer, explained, is the back.
Review a little each day
Grade each card Again, Hard, Good or Easy. Cards you miss come back in minutes; cards you know wait days, then weeks. 20 new cards a day, more on request.
What the deck does for you
Flashcards from your own PDF, each one shown on the day you need it.
Spaced repetition, built in
Each card is scheduled from your grades with SM-2, the classic spaced-repetition method: minutes, then days, then weeks, up to a year. Only the cards that are due show.
Answers that explain themselves
The back of every card says why the answer is right, so a card you miss teaches you something instead of just marking you down.
No cards to write
The cards cover the whole document, chapter by chapter, with more on the important ideas and fewer on the asides. You can start reviewing the day you upload.
A deck that is also a game
The same cards play as an RPG, a platformer, mini-games and duels, sharing your XP, and a card you miss is asked again in battles.
Why spaced flashcards work
Research on learning rates testing yourself and spacing your reviews among the most useful study techniques. A flashcard deck does both.
Retrieval practice
Every battle is a test, and testing beats rereading.
A 2013 review of ten study techniques rated practice testing and spacing the most useful, rereading and highlighting among the least. Tested students remembered more a week later than rereaders.
Dunlosky et al., 2013Spacing
Missed questions come back later, and flashcards are scheduled over days.
Across 317 experiments, spaced study beat one sitting, and the best gap grew with how long the memory had to last. Cramming works for tomorrow and fails in four weeks.
Cepeda et al., 2006Feedback right away
Every answer shows you the right one, and why.
Feedback after a test raises what you keep, and not only on the wrong answers: it also fixes the right ones you were unsure of, which slip away first.
Butler, Karpicke & Roediger, 2008Motivation you can feel
Levels, bosses and streaks make your progress visible.
People stick with what makes them feel competent and lets them choose. A rising level and a fallen boss are competence you can see; five modes are the choice.
Ryan & Deci, 2000- Dunlosky, Rawson, Marsh, Nathan & Willingham (2013). Improving students’ learning with effective learning techniques: promising directions from cognitive and educational psychology. Psychological Science in the Public Interest, 14(1), 4–58.
- Roediger & Karpicke (2006). Test-enhanced learning: taking memory tests improves long-term retention. Psychological Science, 17(3), 249–255.
- Cepeda, Pashler, Vul, Wixted & Rohrer (2006). Distributed practice in verbal recall tasks: a review and quantitative synthesis. Psychological Bulletin, 132(3), 354–380.
- Butler, Karpicke & Roediger (2008). Correcting a metacognitive error: feedback increases retention of low-confidence correct responses. Journal of Experimental Psychology: Learning, Memory, and Cognition, 34(4), 918–928.
- Ryan & Deci (2000). Self-determination theory and the facilitation of intrinsic motivation, social development, and well-being. American Psychologist, 55(1), 68–78.
When another tool fits better
Three cases where you want something else.
You want to write or edit every card
The deck is written for you. You can report a card but not rewrite it; Lifetime Pro adds up to 200 cards of your own per world.
You need the cards elsewhere
There is no export to print or to another flashcard app: the deck lives here, on the web and in the Android app.
The cards need pictures
Cards are text only. A diagram, a map or an anatomy plate does not become an image card, and a scanned PDF with no text layer gives nothing to read.
Built on real books
Live numbers, straight from the database.
Questions
What kind of PDF works?
Is this an AI flashcard maker?
How does the spacing work?
How many cards will I get?
Can I study on my phone?
Is it free?
Can I add my own cards?
See also
Free to start
Play the free worlds for as long as you like. Pay once when you want your own books in.
- Unlimited play on free public worlds
- A taste of premium worlds: 5 battles, 10 tower questions and 10 mini-game questions each
- Live duels with friends, classmates or the computer
- All five modes, on any device
- Progress saved to your account
Launch price for the first 100 buyers or until 31 Dec 2026, then $49.99. 97 of 100 left.
- Turn your own notes into games (3 book-to-game credits)
- Unlimited battles on every world
- Unlimited mini-game questions on every world
- Duels on every map of every premium world
- Every premium world, every map, all five modes
- Your own flashcards in any world (up to 200)
- Study timer extras: room themes, window views, pets and focus insights
- Classrooms: share the worlds you generate with your students, who join free
- All future updates included
Need more later? Extra book-to-game credits are $4.00 each, 5% off from 3, 10% off from 5 and 20% off from 10.