# Diffy

> Diffy offers 20 free educational browser games for kids and illustrated books for curious kids and teens. Try the first level of every game without an account. No ads or downloads.

## Site information

- [About Diffy](https://diffy.ai/about): Access, pricing, age guidance, devices, and classroom use.
- [Home](https://diffy.ai/): Try four randomly featured games; browse the full game list.
- [Books library](https://diffy.ai/books): All published books and chapters.
- [Sitemap](https://diffy.ai/sitemap.xml): Canonical public pages.

What is Diffy? Diffy offers 20 free educational browser games for kids and illustrated books for curious kids and teens. Try the first level of every game without an account. No ads or downloads.

Do I need an account? The first level or introductory activity of every game is available without signing in. A grown-up signs in and chooses a player to unlock more levels and save progress. Public books can be read without an account.

Is Diffy free? The games and books are free. Diffy has no ads. It measures product use through Firebase/Google Analytics and Vercel Analytics to improve the service.

Who are the games for? The games cover different ages and subjects. Each game page lists its suggested age range, skills, and how to play. Those age ranges are guidance for choosing an activity, not an assessment of a child's ability.

Can I use Diffy at home or in a classroom? A family or teacher can open a game or book in a browser and use it as an activity. Saved progress uses individual player profiles under a grown-up account. Diffy does not currently offer school rostering, an LMS integration, or a classroom administration dashboard.

What do I need to play? An internet connection and a modern web browser; no app installation is required. Typing and coding activities work best with a physical keyboard. Games use English instructions; Amigo practices Spanish vocabulary.

## Games

- [Data Detective](https://diffy.ai/games/datadetective): Suggested 12+ with support; teens and adults. Investigate rates, outliers and experiments in six market case files. Skills: Compare conversion rates with unequal denominators; Calculate means and medians and interpret an outlier; Allocate a proportional sample and identify selection bias; Distinguish percentage-point change from relative increase; Choose a stronger experimental assignment and acknowledge uncertainty; Apply observed rates to a forecast with explicit limitations.
- [Algebra Workshop](https://diffy.ai/games/algebraworkshop): Suggested 12+ with support; teens and adults. Balance equations, build functions and make a feasible production plan. Skills: Preserve equality by applying an operation to both sides; Undo a scale and an offset in a two-step equation; Construct a linear function from input-output observations; Find values satisfying two simultaneous equations; Separate fixed and variable terms in a cost model; Find minimum whole-unit production that meets a target within capacity.
- [Enterprise Simulator](https://diffy.ai/games/enterprisesimulator): Suggested 12+ with support; teens and adults. Run a play-money stall, reconcile its accounts and plan for uncertainty. Skills: Distinguish revenue, contribution, costs and operating profit; Construct an affordable price and stock plan; Reconcile cash, durable inventory, debt and owner equity; Compare expected profit across possible demand outcomes; Calculate whole-unit break-even and target-profit sales; Compare contribution per visitor and state a forecast's limitations.
- [TypeQuest](https://diffy.ai/games/typequest): Ages 6–12. A touch-typing adventure across six worlds. Skills: Correct home-row finger placement, starting with the F and J anchor keys; Which finger reaches every letter, number, and symbol key; Proper Shift technique for capital letters and symbols; Punctuation and symbols: periods, commas, quotes, and $ % & @ # + - = *; Real typing speed and accuracy on the 100 most common English words; A confidence boost with a bonus Code Cavern (brackets, camelCase, tiny programs).
- [Cortex](https://diffy.ai/games/cortex): Ages 7–14. Quick brain games that sharpen focus and memory. Skills: Working memory through digit span (forward and reverse) and N-back sequences; Selective attention and impulse control with a Stroop color-word challenge; Mental flexibility and task-switching with rules that flip mid-game; Processing speed and sustained focus in fast match rounds; Visual-spatial reasoning through mental rotation and odd-one-out; Quick word skills by unscrambling common letters into real words.
- [Prickly Pot](https://diffy.ai/games/pricklypot): Ages 7–12. Guide Pip through cozy mazes full of switches, hazards, and moving foes. Skills: Spatial planning by comparing routes through a grid maze; Sequencing — collecting every required item before reaching the goal; Cause and effect through flower switches, wooden gates, keys, and golden gates; Timing and self-control around bugs and boulders that keep moving in real time; Strategic use of waiting, shields, and freeze power-ups; Efficiency by replaying patches to beat the par route and improve a best score.
- [MathBlast](https://diffy.ai/games/mathblast): Ages 6–13. Fast, friendly drills that build real arithmetic fluency. Skills: Addition, subtraction, multiplication, and division facts; Comparing numbers and reasoning on a number line, including negatives; Reading, comparing, and finding equivalent fractions; Decimal place value, comparison, and addition and subtraction; Finding a percent of a number and converting percents, fractions, and decimals; Order of operations and times-table mastery up to 12.
- [CodeCritters](https://diffy.ai/games/codecritters): Ages 7–12. Guide a critter with visual code — loops and all, no typing. Skills: Sequencing — putting commands in the right order to trace a path; Loops — replacing repeated steps with a single Repeat block; Nested loops — a loop inside a loop; Conditionals — If and If-Else that sense the tile ahead and branch; Functions — defining a mini-program once and calling it again and again; Debugging and efficiency — fixing broken programs and solving in the fewest blocks.
- [CoinQuest](https://diffy.ai/games/coinquest): Ages 5–11. Make change, save, spend and give — with play money. Skills: Recognizing and ranking US coins and bills by value; Making an exact amount and giving change with the fewest pieces; Budgeting a weekly allowance across needs, wants, and savings; Comparing unit prices to find the genuinely best deal; Working out earnings from a pay rate and hours worked; Reaching a savings goal and a first, gentle look at simple interest.
- [Amigo](https://diffy.ai/games/amigo): Ages 6–12. Learn Spanish words and phrases with pictures and audio. Skills: Spanish words across colors, numbers, animals, food, family, body, and more; Numbers from 0 to 20 and by tens to 100; Common action verbs in their infinitive form; Noun gender and the articles el, la, los, and las, including tricky exceptions; Building correct sentences like "El gato come pescado"; Greetings, polite phrases, and natural replies in mini-conversations.
- [MindMaze](https://diffy.ai/games/mindmaze): Ages 8–14. Sudoku, nonograms and deduction puzzles that level up. Skills: Pattern recognition — arithmetic, geometric, Fibonacci, and alternating sequences; Constraint solving and elimination in 4x4, 6x6, and full 9x9 Sudoku; Deductive reasoning from written clues in logic-grid puzzles; Line-by-line logic to reveal hidden pictures in nonograms; Planning ahead and state reasoning in Lights Out; Spatial planning and sequencing in Sokoban crate puzzles.
- [GlobeTrek](https://diffy.ai/games/globetrek): Ages 7–12. Flags, capitals and continents — explore the whole world. Skills: Matching flags to countries, both flag-to-name and name-to-flag; Recalling capital cities in both directions; Placing countries and physical features on the correct continent; Identifying famous landmarks by country; Learning oceans, major rivers, and mountain peaks; Comparing countries by area and population, plus currencies and languages.
- [WonderLab](https://diffy.ai/games/wonderlab): Ages 6–11. Space, animals, the body and more — explore, classify, quiz. Skills: Space: the planets and their order, day and night, moon phases, and seasons; Animals: vertebrates and invertebrates, animal groups, and life cycles; The human body: the heart, lungs, brain, organ systems, and digestion; Plants and ecology: parts of a plant, photosynthesis, and food-chain roles; Physical science: states of matter, floating and sinking, and pushes and pulls; Earth science: the rock cycle, clouds, the water cycle, and storm safety.
- [NoteQuest](https://diffy.ai/games/notequest): Ages 6–12. Read notes, train your ear and tap out rhythms. Skills: Naming notes on the treble and bass staff, including ledger-line notes; Identifying intervals by ear and telling major from minor; Hearing and repeating short melodies and steady beats; Tapping back rhythms with rests and dotted notes; Reading key signatures and naming the major key; Building major scales with the whole-and-half-step pattern, plus tempo and dynamics terms.
- [Vertex](https://diffy.ai/games/vertex): Ages 9–15. Spin angles, hunt symmetry and plot coordinates — geometry you can play. Skills: Classifying, estimating, and calculating angles with the key angle rules; Identifying polygons and their interior and exterior angle sums; Symmetry and rigid transformations: translation, rotation, and reflection; Plotting and reading points across all four quadrants of the coordinate plane; Measurement: perimeter, area, circle formulas, volume, and surface area; Advanced reasoning: the Pythagorean theorem, similar triangles, and 3D nets.
- [GeneLab](https://diffy.ai/games/genelab): Ages 11–16. From the atoms of life to DNA, RNA and proteins — build life's molecules. Skills: The elements of life (CHNOPS) and how a nucleotide is assembled; Base-pairing rules (A-T, G-C, and A-U in RNA) and hydrogen bonding; Transcription and reading mRNA in codon triplets using the genetic code; Translation and how peptide bonds link amino acids into proteins; The four levels of protein structure and how enzymes work; How point mutations are classified and how one base change causes sickle-cell.
- [AtomForge](https://diffy.ai/games/atomforge): Ages 11–16. Build atoms, charge ions and snap molecules together — chemistry, hands-on. Skills: Atomic structure: protons, neutrons, electrons, and mass number; Electron-shell filling (2, 8, 8) and finding valence electrons; Ions, isotopes, and naming, plus the octet rule; Ionic and covalent bonding and balancing chemical formulas; How the periodic table is organized by groups, periods, and reactivity; Balancing equations, reaction types, the pH scale, and polyatomic ions.
- [QuarkQuest](https://diffy.ai/games/quarkquest): Ages 12–16. Smash atoms, meet quarks and hunt the Higgs — the universe's smallest LEGO. Skills: The building blocks of matter: six quarks and six leptons in three generations; How quark charges add up to make protons and neutrons; The four fundamental forces, their strengths, ranges, and carrier particles; What antimatter is, and why particles and antiparticles annihilate; How beta decay conserves charge and produces a neutrino; The story of the early universe from the first second to the first stars.
- [Kinetix](https://diffy.ai/games/kinetix): Ages 9–14. Launch, balance, roll and crash — real physics you can play with. Skills: How balanced and unbalanced forces set whether and how fast things move; That in a vacuum all masses fall together, and that density decides floating or sinking; Key relationships as intuition: springs, pressure, levers, and work; How energy transforms but is conserved, and how friction bleeds it away; Momentum in collisions, and elastic versus inelastic crashes; Projectile and orbital motion: how angle and speed set range and orbit.
- [FeynLab](https://diffy.ai/games/feynlab): Ages 13–18. Read Feynman diagrams, hunt the Higgs and meet the exotic particle zoo. Skills: The visual grammar of Feynman diagrams: fermion, photon, gluon, weak, and Higgs lines; How forces act by exchanging virtual carrier particles; Quark content and charge of hadrons like the proton, pion, and omega; Testing reactions against conservation of charge, lepton number, and baryon number; Spin and statistics: fermions and the Pauli exclusion principle versus bosons; The Higgs field and discovery — with hypotheses like supersymmetry clearly flagged as unconfirmed.

## Books and chapter text

Each chapter page contains the illustrated reader and an expandable HTML text version with the published captions and dialogue. The chapter URL is the canonical citation target.

### The Human Story

A graphic-novel journey through the science of who we are and where we come from — starting with the spark that set Homo sapiens apart.

- [The Cognitive Revolution](https://diffy.ai/books/the-human-story/the-cognitive-revolution): Around 70,000 years ago, something changed in the way Homo sapiens thought and talked. This chapter follows one band through the night everything shifted — and traces the same idea all the way to today. Approximately 6 minutes.
- [The Agricultural Revolution](https://diffy.ai/books/the-human-story/agricultural-revolution): About 12,000 years ago, in the hill country of the Fertile Crescent, people began planting the wild grain they once only gathered. Follow one farmer's family through a season of harvest and hunger, surplus and toil, as a reliable crop reshapes their bodies, their village, and their freedom to ever walk away. Approximately 6 minutes.
- [Imagined Orders](https://diffy.ai/books/the-human-story/imagined-orders): As farming surpluses swelled into the first cities, humans faced a new problem: how do tens of thousands of strangers cooperate at all? Follow Ishara, a temple scribe in an early Mesopotamian city, as she presses the marks that turn grain, debt, and law into shared fictions powerful enough to bind a civilization — and sometimes bind a person. Approximately 6 minutes.
- [The Unification of Humankind](https://diffy.ai/books/the-human-story/unification-of-humankind): For most of history, humanity lived in thousands of separate small worlds. Follow a long-distance trader across dusty roads and crowded ports as money, empires, and universal beliefs slowly — and not always gently — merge them into one. Approximately 6 minutes.
- [The Scientific Revolution](https://diffy.ai/books/the-human-story/scientific-revolution): About 500 years ago, a new habit of mind took hold: admitting what we didn't know, then going to find out. Follow an apprentice-naturalist as he learns to trust careful observation over old authority — and discovers that the same curiosity that mapped the world also helped conquer it. Approximately 6 minutes.
- [The Anthropocene](https://diffy.ai/books/the-human-story/the-anthropocene): In the blink of an eye by evolutionary standards, humans went from campfires to satellites — and became a force that reshapes the planet itself. Follow Ada and Kessa to the edge of now, and the open question waiting on the other side. Approximately 6 minutes.

### The Examined Life

A graphic-novel introduction to philosophy — starting with the ancient question of what's real, and what it costs to find out.

- [The Cave](https://diffy.ai/books/the-examined-life/the-cave): Prisoners have watched shadows on a wall their whole lives and call it the world. When one of them is dragged into the light, he learns what's real — and has to decide whether to go back and tell the others. Approximately 6 minutes.
- [The Gadfly](https://diffy.ai/books/the-examined-life/the-gadfly): In the noisy markets of ancient Athens, Socrates stopped confident people and asked what they really knew. He wrote nothing, annoyed the powerful, and faced a death sentence with astonishing calm — all to defend one idea: the unexamined life is not worth living. Approximately 6 minutes.
- [The Good Life](https://diffy.ai/books/the-examined-life/the-good-life): Mira visits Aristotle's Lyceum, the school that taught while walking. There she learns that happiness is not a feeling to chase but a way of living you build by habit, one small daily choice at a time. Approximately 6 minutes.
- [The Doubter](https://diffy.ai/books/the-examined-life/the-doubter): In a snowbound Dutch room, René Descartes decides to doubt everything he possibly can — his senses, his memories, even whether he is awake — to see if anything at all can survive. One surprising thing does: the doubting itself. Approximately 6 minutes.
- [The Trolley](https://diffy.ai/books/the-examined-life/the-trolley): A tram is loose, and five lives stand against one. Mira and two friends use a famous thought experiment to meet the two great answers to a single question: how do we decide what is right? Approximately 6 minutes.
- [The Inner Citadel](https://diffy.ai/books/the-examined-life/the-inner-citadel): The Stoics faced storms, slavery, and empire — and found freedom in one hard question: what is actually up to me? Meet Epictetus and Marcus Aurelius, then gather the whole examined life into a single way of walking. Approximately 6 minutes.

### Made by Design

Why does the world look the way it does? A designer and a curious kid pull apart the made world — from door handles to factories to curb cuts — and learn to see (and revise) the designs all around us.

- [Everything Is Designed](https://diffy.ai/books/made-by-design/everything-is-designed): Nothing around you got made by accident - not the door handle, not the chair, not the toothbrush in your bag. This chapter follows one ordinary kitchen tool, the OXO peeler, to show how good design solves real problems for real hands. Approximately 6 minutes.
- [The Design Process](https://diffy.ai/books/made-by-design/the-design-process): Rio and Milo redesign a water bottle for a long-distance hiker, and nothing works on the first try. Along the way they learn the five modes of design: empathize, define, ideate, prototype, and test, a loop you walk again and again. Approximately 6 minutes.
- [Material World](https://diffy.ai/books/made-by-design/material-world): Every material is a bundle of trade-offs, and every shape starts as a process. Rio and Milo compare metal, plastic, wood, and glass, then head into a real factory to watch molds, presses, extrusion lines, and 3D printers turn raw material into objects you can hold. Approximately 6 minutes.
- [Good Design, Bad Design](https://diffy.ai/books/made-by-design/good-design-bad-design): A door tricks Milo into shoving instead of pulling, and Rio has a name for that: bad design. Together they explore affordances, ergonomics, honest design, and why Dieter Rams believed less is more. Approximately 6 minutes.
- [Design for Everyone](https://diffy.ai/books/made-by-design/design-for-everyone): A curb cut built for wheelchairs turns out to help almost everyone. Rio and Milo follow that idea into broken gadgets, glued-in batteries, and the right to repair, then close the book together. Approximately 6 minutes.

### How Not to Be Fooled

A graphic-novel crash course in evidence — maps that skip the ducks, averages that describe nobody, and headlines that skip the third wheel. A statistician and a curious kid learn to ask: who did we count, compared with what, and what else could be true?

- [The Map Is Not the Place](https://diffy.ai/books/how-not-to-be-fooled/the-map-is-not-the-place): A cartoon park map, a classroom globe, and a GPS arrow that points into the ducks. Jules learns the first rule of not being fooled: a model is a tool, not the world. Approximately 6 minutes.
- [Who Did We Ask?](https://diffy.ai/books/how-not-to-be-fooled/who-did-we-ask): Three friends, a pizza line, a wartime airplane, and a ladle of soup. Jules learns that the first question under any big number is: who did we actually count? Approximately 6 minutes.
- [The Average That Lied](https://diffy.ai/books/how-not-to-be-fooled/the-average-that-lied): A thousand-dollar stack, a ghost shoe, and two class photos with the same average height. Jules learns that 'typical' is a family of words — and headlines rarely show ID. Approximately 6 minutes.
- [Together Is Not Because](https://diffy.ai/books/how-not-to-be-fooled/together-is-not-because): Ice cream and swimming, roosters and sunrise, storks and chimneys. Jules learns that two numbers rising together is a clue — and 'because' is a word that has to earn a badge. Approximately 6 minutes.
- [The Rare and the Loud](https://diffy.ai/books/how-not-to-be-fooled/the-rare-and-the-loud): Sharks on magazine covers, a jar of marbles, a screening test, and a thirty-percent chance of rain. Jules learns to start with how common a thing was — before the drama arrives. Approximately 6 minutes.
- [One Study Is Not a Law](https://diffy.ai/books/how-not-to-be-fooled/one-study-is-not-a-law): Coin streaks, cherry-picked graphs, a second classroom, and a pocket list of questions. Jules learns that not being fooled means trusting the world a little more than the story — and checking twice. Approximately 6 minutes.

### The Code of Life

A graphic-novel journey into what makes living things alive — from the tiny cities inside you to the four-letter recipe you share with every creature on Earth, and the slow, blind magic that shaped it all.

- [The Smallest City](https://diffy.ai/books/the-code-of-life/the-smallest-city): Under a microscope, a scrap of pond water turns into a crowd of tiny living bubbles. Shrink down inside just one and you find not a blob but a bustling city — a library, power stations, workshops, and a wall with gates — all keeping you alive. Approximately 5 minutes.
- [The Recipe Inside](https://diffy.ai/books/the-code-of-life/the-recipe-inside): Inside most of your body cells that have nuclei sits a copy of the same master book — DNA — spelled with an alphabet of only four letters on a twisted ladder. A simple pairing rule lets DNA copy almost perfectly as cells divide, while different cells use different parts of the book. Approximately 5 minutes.
- [Mistakes and Marvels](https://diffy.ai/books/the-code-of-life/mistakes-and-marvels): Mutations are DNA changes that arise without regard to what an organism needs. Their effects depend on context: many have little or no effect, some are harmful, and a few help in particular environments. Passed down, those differences make adaptation possible. Approximately 5 minutes.
- [The Blind Sculptor](https://diffy.ai/books/the-code-of-life/the-blind-sculptor): Random variation fills a meadow with beetles of many colors. A hungry bird is more likely to catch the ones that stand out, though chance still shapes every hunt. Survivors breed, and over generations the meadow shifts toward beetles that look designed for it. Nobody designed them. Approximately 6 minutes.
- [Deep Time](https://diffy.ai/books/the-code-of-life/deep-time): Read rock layers like pages and you meet vanished ammonites, trilobites, and non-avian dinosaurs, plus fossils that combine ancestral and derived traits. Branching fish lineages illuminate the origin of early four-limbed vertebrates; one theropod branch survives as birds. Tiny changes across deep time built life's branching tree. Approximately 6 minutes.
- [One Family Tree](https://diffy.ai/books/the-code-of-life/one-family-tree): Trace living cellular lineages backward and they converge on an ancient ancestral population. Shared DNA letters and deeply conserved cellular machinery are clues among many: a bacterium, an oak, a mushroom, and you belong to one branching family, living tangled together still. Approximately 6 minutes.

### Inside Your Head

A graphic-novel tour of your own mind — how attention aims like a spotlight, how seeing is really guessing, how memory rebuilds instead of records, how feelings carry messages, how practice wears a path, and how handy mental shortcuts can quietly fool anyone. A cognitive neuroscientist and a curious kid rehearse a library science night, one puzzle at a time.

- [The Spotlight Has Edges](https://diffy.ai/books/inside-your-head/the-spotlight-has-edges): Setting up the first science-night table, Noor discovers that paying attention is like aiming a spotlight: it lights one thing brilliantly, blurs the edges, misses what it isn't pointed at, and costs a beat every time it jumps. And a calmer room helps more than trying harder. Approximately 5 minutes.
- [More Than Meets the Eye](https://diffy.ai/books/inside-your-head/more-than-meets-the-eye): At the optical-tricks table, Noor learns her eyes never send the whole picture. Her brain fills the gaps, reads through context, and keeps the world steady — brilliant work that can also be fooled in honest, predictable ways many people experience. Approximately 5 minutes.
- [The Workbench and the Archive](https://diffy.ai/books/inside-your-head/the-workbench-and-the-archive): A tiny workbench and a giant card catalog show Noor that memory isn't a video. A few things fit on the bench at once, only what you work with reaches the archive, and remembering rebuilds the past instead of replaying it. Approximately 5 minutes.
- [Feelings Carry Messages](https://diffy.ai/books/inside-your-head/feelings-carry-messages): When stage-nerves ambush Noor, Dr. Imani treats the feeling as station four. Emotions blend body, story, and situation; they flag what might matter without being facts or commands — and big, lasting distress is a signal to find a trusted adult. Approximately 5 minutes.
- [Building a Path](https://diffy.ai/books/inside-your-head/building-a-path): Noor keeps flubbing a cue, so Dr. Imani builds a path. Durable learning comes from testing yourself, spacing it out, real feedback, mixing it up, and rest — slower to feel, stronger to keep — and the gains stay honest and specific. Approximately 5 minutes.
- [Shortcuts in the Fog](https://diffy.ai/books/inside-your-head/shortcuts-in-the-fog): At the last table, with the doors about to open, Noor meets the mind's shortcuts: anchoring, availability, confirmation, framing, and hindsight. They're fast and usually helpful, they fool everyone, and the fix is humble tools, not just trying harder. Approximately 5 minutes.