Proof Fidget vs SolvedBooks

ProofFidget is a puzzle-driven way to learn the feel of doing math: not by memorizing procedures, but by making correct moves, one step at a time, until a proof truly holds together. Each puzzle gives you a clear goal and a partially-complete derivation. You spin the wheel to choose your next move, then commit to a step and watch the proof line up. If you’re right, you progress; if you’re wrong, you learn quickly why it didn’t fit. The result is a tight feedback loop that makes abstract ideas concrete and surprisingly fun. You’ll work across a growing set of subjects, including: Logic and proof techniques: build confidence with implication, contradiction, and structured reasoning. Algebra: make valid transformations while keeping equations balanced, supported by visual “balance scale” diagrams. Number theory: practice modular arithmetic, divisibility, and gcd-style reasoning with intuitive visuals. Geometry and beyond: use diagrams to ground symbolic steps in something you can see. ProofFidget is designed for short, satisfying sessions, but it also rewards deeper play: you start noticing patterns, choosing steps for the right reasons, and developing proof instincts that transfer to real coursework and problem-solving. If you’ve ever thought “I understand the formula, but I don’t understand why,” ProofFidget is built for that moment.

SolvedBooks is a free study companion for university and graduate students working through classic mathematics textbooks. Every solution is written from scratch by a working mathematician — not scraped, paraphrased, or copied from any publisher's solutions manual. Each exercise gets a complete worked proof in clean LaTeX, plus a brief final-answer summary. Currently covered — 1,400+ exercises: • Serge Lang — Undergraduate Algebra, 3rd Edition • Sheldon Axler — Linear Algebra Done Right, 4th Edition • John M. Lee — Introduction to Smooth Manifolds, 2nd Edition (GTM 218) • John M. Lee — Riemannian Manifolds: An Introduction to Curvature (GTM 176) How it works Question groups (5 exercises each) are locked by default. Tap "Watch ad to unlock" once per group and the unlock is permanent on your device. There is no in-app purchase to remove ads — the ads pay to maintain the app and cover more textbooks over time. What you will not find here • The original textbook problem statements — they are intentionally not reproduced • Hints, figures, or solutions copied from any publisher's manual • Accounts or cross-device sync — v1 is local-only and works offline Pen before Peek Please attempt each exercise yourself first. Productive struggle is where the mathematics lives. SolvedBooks is for the moments where you genuinely need a worked solution to keep moving forward, not a shortcut around the thinking. About the developer Built by Chris Pun, a math graduate working in differential geometry. If you find an error in a solution, or want a particular textbook covered, please get in touch — every piece of feedback is read. Independent study aid. Not affiliated with or endorsed by Springer, Pearson, Addison-Wesley, or any other publisher. All textbook titles, author names, and chapter references are used solely for identification.