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Free beginner gogolangconcurrency

Go: Zero to Production

Learn Go from variables, control flow, and functions through slices, maps, structs, interfaces, error handling, and pointers, then concurrency, generics, the standard library, and building a tested HTTP service. Run and edit real Go in your browser (compiled to WebAssembly), with a graded exercise in every lesson.

📚 72 lessons ⏱ 783 min 🎬 3 ⚡ 72 exercises
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Free intermediate mathlinear-algebra

Linear Algebra

Vectors, matrices, eigenvalues, and the geometry that ties them together — from Gaussian elimination through spectral theory to PCA, graphs, and differential equations.

📚 51 lessons ⏱ 500 min ⚡ 51 exercises
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Free advanced calculusmathdifferential-equations

Advanced Calculus Topics

Three tracks for after Calculus I-III: differential equations, calculus for machine learning (gradient descent, backprop, autodiff), and a rigorous bridge to real analysis.

📚 25 lessons ⏱ 259 min ⚡ 25 exercises
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Free intermediate calculusmathematicsvector-calculus

Calculus III: Multivariable & Vector Calculus

Vectors and space curves, partial derivatives and the gradient, multiple integrals and the Jacobian, then vector fields up to Green's, Stokes' and the divergence theorem -- unified at the end as one theorem. Runnable Python throughout.

📚 32 lessons ⏱ 327 min ⚡ 32 exercises
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Free intermediate calculusmathintegrals

Calculus II: Integrals & Series

Integration and its applications, parametric and polar calculus, and sequences and series — antiderivatives through the Fundamental Theorem, integration techniques, volumes and arc length, and Taylor series.

📚 41 lessons ⏱ 457 min ⚡ 41 exercises
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Free beginner calculusmathderivatives

Calculus I: Limits & Derivatives

Where calculus starts: limits, continuity, and the derivative — built from the definition up through the product, quotient, and chain rules, then put to work on related rates, curve sketching, and optimization.

📚 35 lessons ⏱ 485 min ⚡ 35 exercises
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Free intermediate statisticsprobabilitydata-science

Probability & Statistics

From describing data to Radon-Nikodym derivatives: probability, random variables, limit theorems, estimation, hypothesis testing, regression, Bayesian inference, stochastic processes, information theory and Monte Carlo. Teaches the misuse of each tool as carefully as the tool. Assumes basic calculus.

📚 67 lessons ⏱ 928 min 🎬 67 ⚡ 67 exercises
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Free intermediate pysparksparkdataframes

PySpark: Practical DataFrames

Learn PySpark by writing it - the DataFrame API end to end: select and filter, aggregation, joins, window functions, complex/nested data, Spark SQL, and reading/writing files. Every code box runs right in your browser (real pyspark.sql on DuckDB), with a graded exercise in every lesson.

📚 44 lessons ⏱ 175 min ⚡ 44 exercises
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Free beginner sqlpostgresqldatabases

SQL: Zero to Production

Learn SQL from the ground up: query data, create tables, and change data, then joins, aggregation, subqueries, window functions and more. Run and edit the SQL from every module right in your browser, with a graded exercise in every lesson.

📚 55 lessons ⏱ 408 min ⚡ 55 exercises