Tech WondersPlay

The path

Every zone, every lesson

Each zone is a tech place with nine lessons. Open any lesson to see the question it answers.

180 lessons20 zones

1Zone 1

Origin Core

Open the zone
  1. 1Graph TheorySix DegreesYou're about six people away from almost anyone
  2. 2ProbabilityThe Birthday SurpriseWith just 23 people, a shared birthday is more likely than not
  3. 3Coding TheoryBroken QR Codes Still WorkRip out part of a QR code and it can still scan
  4. 4Map ProjectionsMercator's LieGreenland looks as big as Africa; Africa is 14 times bigger
  5. 5GeographyWhy Flights CurveThe shortest route looks bent on a flat map
  6. 6Natural Language ProcessingWhy AI Can't Count the R's in StrawberryAI reads chunks of words, not letters
  7. 7Internet & WebJourney of a ClickTap a link and your request circles the planet in under a second
  8. 8Visual PerceptionThe Blind SpotThere's a hole in your vision and your brain paints over it
  9. 9InfinityHilbert's HotelA full hotel with infinitely many rooms can always fit more guests
2Zone 2

Firewall Keep

Open the zone
  1. 10ProbabilityThe Monty Hall TrapSwitching doors doubles your chance of winning the car
  2. 11Computer Arithmetic0.1 + 0.2 ≠ 0.3Computers get simple decimal sums slightly wrong
  3. 12Digital PrivacyYour Photos Know Where You LiveMany phone photos carry hidden GPS coordinates
  4. 13Digital MediaMovies Don't MoveFilms are still pictures shown fast enough to fool you
  5. 14Social EngineeringThe Phishing HookThe most dangerous hack attacks your judgment, not your computer
  6. 15CombinatoricsYour Shuffle Has Never Happened BeforeA well-shuffled deck is almost certainly a first in history
  7. 16Artificial IntelligenceConfidently WrongAI can sound certain while inventing an answer
  8. 17Color PerceptionThe DressYour brain guesses the lighting before deciding what color it sees
  9. 18Software HistoryGangnam Style Broke YouTube's CounterA video got more views than the counter could count
3Zone 3

Turbine Ridge

Open the zone
  1. 19ProbabilityShuffle Isn't RandomSpotify made shuffle less random because the real thing felt rigged
  2. 20Data StorageDeleted Isn't GoneDeleting a file usually just erases its address, not its contents
  3. 21GeometryThe Rope Around the EarthAdd one meter to a rope around the planet and it lifts 16 cm everywhere
  4. 22AttentionThe Invisible GorillaHalf of people miss a gorilla walking through a basketball game
  5. 23VideoThe Wagon-Wheel EffectWhy wheels spin backwards in videos
  6. 24GeometryThe Missing SquareRearrange the same pieces and a square appears from nowhere
  7. 25ProgrammingThe Fencepost PuzzleA 10-meter fence with a post every meter needs 11 posts
  8. 26Exponential GrowthFold Paper to the MoonFold a sheet 42 times and it would reach the Moon
  9. 27AeronauticsHow Planes Really FlyThe famous ‘longer path over the top’ explanation is wrong
4Zone 4

Cipher Vault

Open the zone
  1. 28Web TechnologyThe Cookie JarA tiny note lets a website remember you were here
  2. 29Account SecurityTwo-Factor LoginA stolen password is nearly useless without the second key
  3. 30Classical CryptographyCaesar's CipherJulius Caesar hid messages by shifting every letter three places
  4. 31CodebreakingCounting Letters Breaks CodesA 9th-century scholar cracked substitution ciphers with a tally chart
  5. 32Classical CryptographyThe Unbreakable Cipher That BrokeVigenère's code was called indecipherable for 300 years
  6. 33CryptographyThe Secret HandshakeTwo strangers can agree on a secret while everyone listens
  7. 34Quantum PhysicsThe Quantum TunnelParticles can cross walls they can't climb, and your phone's memory relies on it
  8. 35Energy StorageWhy Your Battery Wears OutHeat, full charges and empty batteries age your phone fastest
  9. 36Data StorageWhy Your 1 TB Drive Shows 931 GBDrive makers and computers count bytes differently
5Zone 5

Quantum Foam

Open the zone
  1. 37Data CommunicationThe Packet PuzzleYour message is chopped up and rebuilt at the other end
  2. 38Digital ImagingRolling ShutterWhy your phone bends propellers into banana shapes
  3. 39AlgorithmsGuess My Number in 7 TriesBinary search halves the possibilities to find your number fast
  4. 40Civil EngineeringWhy Concrete Needs SteelConcrete is strong under squeezing and weak under stretching
  5. 41ProbabilitySpot the Fake Coin FlipsPeople faking random flips almost never write long streaks
  6. 42Error DetectionYour Card's Last Digit Is a Lie DetectorThe final digit of a card number checks all the others
  7. 43Computing HistoryThe 1890 Census Ran on Punch CardsHoles in cardboard counted a nation, and IBM grew from it
  8. 44Quantum MechanicsThe Double-Slit SurpriseSingle particles build a pattern only waves should make
  9. 45Machine LearningNearest NeighborA new item can be classified by the examples most like it
6Zone 6

Silicon Dunes

Open the zone
  1. 46Digital PsychologyPhantom VibrationsMost phone users have felt a buzz that never happened
  2. 47AstronomyWhy We Only See One Side of the MoonThe Moon spins exactly once per orbit
  3. 48CombinatoricsThe Pigeonhole TrickToo many pigeons for the holes guarantees a hidden match
  4. 49Online PrivacyIncognito Isn't InvisiblePrivate mode hides your history from your phone, not from the internet
  5. 50Online SafetyThe QR Sticker ScamA fake code taped over the parking meter sends your card to a thief
  6. 51Cryptographic HashingChange One Letter, Change EverythingA hash is a fingerprint that flips totally at the smallest change
  7. 52BinaryEverything Is BinarySongs, photos and this sentence are all just ons and offs
  8. 53Atomic PhysicsAtoms Are Mostly EmptyIf an atom were a stadium, the nucleus would be a marble
  9. 54Thermal EngineeringYour Fridge Doesn't Make ColdIt pumps heat out of the box and dumps it into your kitchen
7Zone 7

Fiber Reef

Open the zone
  1. 55Programming ConceptsThe Peanut Butter RobotProgramming is giving instructions with zero common sense
  2. 56Digital ImagingWhy Your Selfie Is FlippedYour front camera shows a mirror, then saves the truth
  3. 57AlgorithmsSorting RaceThe right method beats a faster computer
  4. 58Fiber OpticsLight That Bends Around CornersLight can be trapped inside a glass thread
  5. 59Internet InfrastructureThe Undersea InternetAlmost all intercontinental data travels through cables on the ocean floor
  6. 60Automotive SafetyCrumple ZonesCars protect people by crushing slowly
  7. 61ProbabilityThe Gambler's FallacyAfter five heads, the coin still has no memory
  8. 62Data EncodingBarcodesBlack and white stripes are just numbers in disguise
  9. 63Web HistoryThe First Website Is Still OnlineYou can still visit the page Tim Berners-Lee published in 1991
8Zone 8

Pixel Drift

Open the zone
  1. 64Computer NetworksFinding a RoutePackets cross the planet without anyone knowing the whole map
  2. 65Data AnnotationYou've Been Training AI for FreeThose CAPTCHA traffic lights and crosswalks taught machines to see
  3. 66Pattern PerceptionFaces EverywhereYour brain is so tuned to faces it finds them in plugs and toast
  4. 67SpaceflightSixteen Sunrises a DayThe space station circles Earth every 90 minutes
  5. 68CombinatoricsThe Party PuzzleAt any party of six, three are all friends or all strangers
  6. 69Internet TrafficHalf the Internet Is RobotsNearly half of all web traffic is not human
  7. 70Social EngineeringWould You Plug It In?Nearly half of dropped USB sticks got plugged in
  8. 71AcousticsThe Sonic BoomOutrun your own sound and it piles up into a shock wave
  9. 72Color ScienceThe Missing YellowYour screen shows yellow without a single yellow light
9Zone 9

Circuit Grove

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  1. 73Computer ArchitectureThe Desk and the WarehouseComputers keep a tiny super-fast memory for what you'll need next
  2. 74Reliable NetworkingThe Lost PacketMissing pieces are requested again without restarting everything
  3. 75Visual EffectsWhy Weather Presenters Never Wear GreenOne color can be replaced with an entire world
  4. 76RecursionThe Tower of HanoiMoving 64 disks would take longer than the universe has existed
  5. 77Safety EngineeringOtis Cut the RopeElevators became safe when one inventor cut his own cable in public
  6. 78Graph TheoryThe Bridges of KönigsbergA Sunday-stroll puzzle invented a whole branch of math
  7. 79ProbabilityThe Sticker Album ProblemFinding the last few stickers takes longer than the rest combined
  8. 80Audio EngineeringThe Phantom SingerTwo speakers can put a voice where there's no speaker at all
  9. 81Internet HistoryThe Internet's First Word Was ‘LO’The first message crashed after two letters
10Zone 10

Analog Foundry

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  1. 82Neural NetworksA Neuron Is a Weighted VoteThe building block of AI is a very simple decision
  2. 83Visual NeuroscienceThe Afterimage FlagStare at the wrong colors and the right ones appear
  3. 84TimekeepingThe Country That Skipped a DaySamoa jumped straight from 29 to 31 December 2011
  4. 85Numbers0.999… = 1The endless nines are exactly one, not ‘almost one’
  5. 86Internet SpeedMegabits, Not MegabytesWhy your ‘100’ connection downloads at about 12
  6. 87Password SecurityEveryone's Password Is 123456The most common passwords fall in under a second
  7. 88ElectromagnetismMeasure Light Speed With ChocolateYour microwave can measure the speed of light
  8. 89Structural DesignThe ArchLoose stones stand for 2,000 years by pushing on each other
  9. 90MultitaskingYour Computer Doesn't MultitaskIt switches between jobs so fast it fools you
11Zone 11

Server Farm

Open the zone
  1. 91Sensor TechnologyWhy Gloves Don't Work on PhonesYour finger changes an electric field, and so does a sausage
  2. 92AlgorithmsThe Hand-on-the-Wall RuleKeep one hand on the wall and you'll escape most mazes
  3. 93GeometryWhy Three Legs Never WobbleThree points always fit a surface; four often don't
  4. 94StatisticsWhen the Average LiesA billionaire walks into a bar and everyone gets rich on average
  5. 95Wave PhysicsThe Doppler EffectMotion changes the pitch of sound and the color of light
  6. 96Cognitive PsychologyThe Stroop EffectSaying the color of a word is hard when the word names another color
  7. 97StatisticsBenford's LawIn real data, numbers start with 1 six times more often than with 9
  8. 98Planetary ScienceA Day on Venus Is Longer Than Its YearVenus spins so slowly the year ends first
  9. 99Recreational MathematicsThe Mysterious 6174Any four-digit number falls into the same number
12Zone 12

Signal Storm

Open the zone
  1. 100Interaction DesignThe Bottomless FeedRemove the bottom of the page and people forget to stop
  2. 101ElectromagnetismWhy Your Microwave Door Has HolesThe holes are too small for microwaves but big enough for light
  3. 102Operating SystemsWhy Restarting Fixes ThingsTurning it off and on again clears what went wrong
  4. 103InfraredYour Camera Sees Your TV RemotePoint a remote at your phone's camera and see the invisible light
  5. 104Wave InterferenceSilence Made of SoundNoise-canceling headphones add sound to make quiet
  6. 105SensorsYour Phone Knows Which Way Is UpA microscopic weight on springs senses every tilt
  7. 106ProbabilityPenney's GameLet me choose second and I'll win most coin-flip races
  8. 107AcousticsWhy You Hate Your Recorded VoiceYou normally hear yourself through your own skull
  9. 108NeuroscienceWhy You Can't Tickle YourselfYour brain predicts your own touch and cancels it
13Zone 13

Retro Terminal

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  1. 109Planetary ScienceSaturn Would FloatThe giant planet is less dense than water
  2. 110FractalsRandom Dots Draw a TriangleA game of chance draws a perfect fractal
  3. 111Text EncodingEmoji Are Secret SumsA family emoji is several emoji glued together
  4. 112WavesCount the ThunderLightning tells you how far away the storm is
  5. 113Engineering DesignWhy Manholes Are RoundA round cover can never fall into its own hole
  6. 114GeometryThe Drill That Makes Square HolesA rounded triangle can drill an almost square hole
  7. 115ProbabilityWhy Casinos Always WinOver enough bets, a small edge becomes a certainty
  8. 116Music AcousticsWhy Some Notes Sound Good TogetherPleasant chords hide simple ratios
  9. 117Computing HistoryThe First Bug Was a Real MothIn 1947 engineers taped a moth into their logbook
14Zone 14

Neural Nexus

Open the zone
  1. 118NeuroscienceHow Fast Are You?Reacting to a light takes about a quarter of a second
  2. 119AstronomyThe Sun Is WhiteIt only looks yellow through our atmosphere
  3. 120NumbersFind Your Birthday in PiPi's endless digits almost certainly hide every date
  4. 121Mobile MessagingWhy Texts Were 160 CharactersAn engineer counted the letters on postcards
  5. 122Social MediaWhy Tweets Were 140Twitter left 20 characters of every text message for your name
  6. 123Language ModelsThe Word-Guessing MachineChatbots write by predicting the next word, again and again
  7. 124OpticsWhy the Sky Is BlueAir scatters blue light far more than red, and sunsets are the leftovers
  8. 125MechanicsGearsTrading speed for force is how bikes climb hills
  9. 126StatisticsThe Bell Curve MachineBouncing balls always pile up into the same shape
15Zone 15

Satellite Belt

Open the zone
  1. 127Auditory PerceptionYanny or Laurel?One recording, two words, and people hear different ones
  2. 128Unsolved ProblemsThe Simplest Unsolved ProblemHalve if even, triple and add one if odd; does it always reach 1?
  3. 129Internet HistoryThe First YouTube VideoNineteen seconds at a zoo started it all
  4. 130BiomimicryThe Train That Copied a BirdJapan's bullet train borrowed its nose from a kingfisher
  5. 131StatisticsWhat ‘70% Chance of Rain’ MeansIt isn't 70% of the day or 70% of the city
  6. 132PerceptionYour Brain Hides Your NoseYour nose is always in view, yet you never see it
  7. 133Precision MeasurementThe Atomic ClockThe most precise clocks count the vibrations inside atoms
  8. 134Satellite NavigationHow GPS Finds YouYour phone listens to satellites' clocks and does the math
  9. 135Mathematics in NatureSunflowers Count in FibonacciSeed spirals come in 34s, 55s and 89s
16Zone 16

Launch Pad

Open the zone
  1. 136Myth-bustingYou Can't See the Great Wall From SpaceThe famous claim is a myth
  2. 137Data VisualizationThe Chart That LiesCut the bottom off an axis and a tiny change looks huge
  3. 138History of ScienceMeasuring the Earth With a StickOver 2,000 years ago a scholar measured the planet with shadows
  4. 139PerceptionThe Three BowlsOne hand says warm, the other says cold, in the same water
  5. 140GeometryWhy Bees Build HexagonsHexagons hold the most honey with the least wax
  6. 141Web TechnologyWhy 404?The famous ‘Not Found’ number is not a room at CERN
  7. 142TopologyThe Möbius StripA loop of paper with only one side and one edge
  8. 143Personal SecurityThe Password ManagerOne strong vault lets every account have its own secret
  9. 144EncryptionThe Only Perfect CipherA one-time pad is unbreakable if you never, ever reuse it
17Zone 17

Cloud Citadel

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  1. 145Exponential GrowthRice on a ChessboardDouble a grain on every square and you'd bankrupt a kingdom
  2. 146Quantum MechanicsSchrödinger's Cat Was a JokeThe famous cat was meant to show how absurd the idea sounded
  3. 147Exponential GrowthThe Lily Pad RiddleIf lilies double daily and cover the pond on day 30, when was it half full?
  4. 148Electrical EngineeringThe Cooktop That Stays ColdInduction heats the pan directly with a changing magnetic field
  5. 149Search EnginesHow Google Ranked the WebA page matters when pages that matter point to it
  6. 150Text EncodingA Is 65Every letter you type is secretly a number
  7. 151Congestion ControlThe Internet's Traffic JamNetworks slow themselves down on purpose to avoid collapse
  8. 152Game DesignWhy Mario Has a MoustacheIn a 16×16 sprite, a moustache was easier to draw than a mouth
  9. 153AlgorithmsTwice the Data, Four Times the WaitHow fast a method slows down is what matters
18Zone 18

Firewall Keep

Open the zone
  1. 154Infinite SeriesAchilles and the TortoiseInfinitely many steps can take finite time
  2. 155Bridge EngineeringSuspension BridgesCables turn huge loads into tension they can handle
  3. 156Recreational MathematicsThe 1089 TrickAny three-digit number leads to the same answer
  4. 157ProbabilityThe 100 Prisoners RiddleA clever plan turns near-certain death into a 31% chance
  5. 158PsychoacousticsWhy Ads Sound LouderTwo sounds at the same volume can feel completely different
  6. 159Computing HistoryThe Women Who Programmed ENIACSix women programmed the first general-purpose electronic computer
  7. 160Language ModelsSame Question, Different AnswerA dial called temperature makes chatbots creative or predictable
  8. 161CryptographyHow Long to Crack It?Every extra character multiplies an attacker's work
  9. 162CybersecurityHow Sites Store Your PasswordA good website never actually knows your password
19Zone 19

Turbine Ridge

Open the zone
  1. 163ArithmeticThe Missing DollarA famous money riddle works by adding the wrong things
  2. 164Auditory PerceptionThe Cocktail Party EffectYour brain can follow one voice in a crowded room
  3. 165GeometryPythagoras Without AlgebraSlide four triangles and the theorem proves itself
  4. 166AstrodynamicsEscape SpeedLeaving Earth for good needs about 11 kilometers a second
  5. 167Internet CultureError 418: I'm a TeapotAn April Fools' joke that became part of real internet standards
  6. 168Electrical EngineeringThe War of the CurrentsEdison and Tesla fought over how electricity should reach your home
  7. 169Password HygieneCredential StuffingOne leaked password can open many unrelated accounts
  8. 170Number TheoryThe Prime LockMultiplying is easy; un-multiplying is the secret behind online security
  9. 171Particle PhysicsGhost ParticlesTrillions of neutrinos pass through you every second
20Zone 20

Cipher Vault

Open the zone
  1. 172Network MathematicsThe Friendship ParadoxYour friends probably have more friends than you do
  2. 173Electric VehiclesBraking Into the BatteryElectric cars recharge a little every time they slow down
  3. 174Game TheoryWinning at Rock-Paper-ScissorsHumans are bad at being random, and a machine can exploit it
  4. 175Binary ComputingThe Vote From Outer SpaceA cosmic ray may have added 4,096 votes in a Belgian election
  5. 176Network PerformanceFast Internet, Slow PagesBandwidth isn't speed; round trips add up
  6. 177Game PhysicsWhy Characters Fall Through WallsGames check for collisions in snapshots, and fast things slip between them
  7. 178Classical CryptographyThe Enigma Machine158 quintillion settings, changed every single day
  8. 179CodebreakingBreaking EnigmaIt fell to habits, guesses and a room full of machines
  9. 180AlgorithmsGreedy ChangeAlways giving the biggest coin usually works, until it doesn't

More zones are on their way.