The atlas
All of mathematics, one shelf at a time
65,844 problems in 17 subjects. Pick a shelf — every subject runs from a gentle first step to its deeper corners.
For everyone
No background needed — just curiosity.
Foundations
The school mathematics everything else is built on.
ArithmeticElementaryFractions, percentages, ratios, and the mental tricks that make numbers feel friendly.22,813 problemsAlgebraHigh schoolEquations, functions, polynomials, inequalities — the grammar of mathematics.26,515 problemsGeometryHigh schoolTriangles, circles, area and angle — Euclid's playground, and a few modern tricks.2,006 problemsTrigonometryHigh schoolSines, cosines, and the circle that ties them together.791 problemsComplex NumbersHigh schoolWhat happens when −1 gets a square root: rotation, roots of unity, and Euler's formula.259 problems
Calculus & beyond
Change, space, and chance — the university core.
CalculusUniversity · year 1Limits, derivatives, integrals and series — the mathematics of change.1,509 problemsMultivariable CalculusUniversity · year 2Calculus in space: partial derivatives, gradients, multiple integrals, and vector fields.725 problemsLinear AlgebraUniversity · year 1–2Vectors, matrices, and linear maps — the most useful mathematics there is.407 problemsDifferential EquationsUniversity · year 2Equations whose unknowns are functions: growth, oscillation, and everything that moves.104 problemsProbabilityHigh school → universityChance, expectation, and the paradoxes that fool our intuition.3,425 problemsStatisticsHigh school → universityLearning from data: describing it, sampling it, and deciding what it really says.1,163 problems
Pure mathematics
Structure and proof, where the deepest ideas live.
Number TheoryOlympiad · universityPrimes, divisibility, and modular arithmetic — the queen of mathematics.3,785 problemsCombinatoricsOlympiad · universityThe art of counting without counting — and graphs, invariants, and pigeonholes.1,928 problemsReal AnalysisUniversity · year 2–3Calculus made rigorous: sequences, series, continuity, and the real line itself.118 problemsComplex AnalysisUniversity · year 3Calculus over ℂ, where every derivative is a miracle and contour integrals do the impossible.50 problemsAbstract AlgebraUniversity · year 3Groups, rings, and fields — symmetry, distilled.50 problems