--- title: "Inside Professor Oops" description: "How Professor Oops is built: a sheet of paper where every tool and animal reads and writes the same heat, water and air, chapter by chapter." source_name: "Game Tailors" source_url: "https://professoroops.com/en/inside/" site_home: "https://professoroops.com/" source_description: "The drawing app where the paper is real. No ads. No accounts. No personal data: only anonymous counts, which you can switch off." locale: "en" legal: - "Game Tailors · Schieweg 15Y-40, 2627 AN Delft (NL)" - "KvK 92437702 · VAT NL866044474B01" - "info@gametailors.com · +31 6 4227 5919" copyright: "© 2026 Game Tailors" published_at: "2026-11-10T12:04:14.297Z" modified_at: "2026-11-10T12:04:14.297Z" --- # Inside Professor Oops ## A sheet of paper where everything follows the same rules Professor Oops gives a child a sheet of paper and 83 real things to try on it: watercolour, ketchup, a match, a fan, a battery, ants. Every tiny spot of the paper keeps its own heat, its own water and what's dissolved in it, and every tool and animal reads and writes those same numbers. So a child can try something nobody planned for and still get a sensible answer. These pages show how that is built. [How it all connects]()[All chapters](<#chapters>)[For engineers](<#hood-engineers>) ![Painted illustration of the painter crouching by an oven, watching a crayon drawing toast golden inside, with an ice-cube tray and a lemon.]() ## A child sees paper and a toolbox; underneath, every speck of the paper is a little world Open Professor Oops and there is a sheet of paper on a table, with drawers full of things from the kitchen, the bathroom, the garden, the craft box, the toy box, the science shelf and the toolbox. There are no levels, no scores and nothing to win. A child paints, pours, squeezes, lights, bangs and waits, and watches what happens. Every result is worked out as it happens. Drop water on a black marker dot and it opens into rings of blue, pink and yellow. Let a fire reach it and the fire is held back at the wet edge until its heat has boiled the water off. Roll a football past a candle and the candle goes out. Leave ketchup out for three days and it grows mould; leave honey out and it doesn't. Each of these comes from a small rule about one thing, such as heat or water or air, applied the same way to everything on the page. That is why the game can surprise the people who made it. A child who combines two things nobody thought of still gets an answer that makes sense, because both things already speak the same language. A sheet of paper where everything follows the same rules For engineers ### A sheet of paper where everything follows the same rules A grid of up to 512 × 384 cells, each about half a millimetre, stepped at a fixed 1/60 s in a Web Worker. A type-checked TypeScript AST scan finds 33 systems sharing 55 per-cell and per-region layers through 689 read and write links, and no rule that names two substances. The busiest loops run as seven WebAssembly kernels, five of them tested bit for bit against their JavaScript twins. At the release the code held 2,614 tests in 270 files. [Under the hood](<#hood-sees>) A child sees paper and a toolbox; underneath, every speck of the paper is a little world Under the hood ### A child sees paper and a toolbox; underneath, every speck of the paper is a little world The sheet is a grid of up to 512 × 384 cells on a large page and 288 × 216 on a phone, each about 0.5 to 0.6 mm. Every cell keeps its own temperature, how wet it is and any water standing on it, its colour as the light it soaks up, the liquids lying on it and floating on them, and a dozen dissolved substances. Air, smells and what animals sense live on a coarser grid \(64 × 48 on a full page\). Loose things such as balls, mugs and cars are 2.5D bodies that all follow the same rules for bumping and rolling. The whole engine steps at a fixed 1/60 s in a Web Worker, away from the screen. The screen draws from a copy of the state and redraws only the parts of the page that changed. Each of the 97 materials at the release is described by numbers in one shared table; the code that moves liquids reads those numbers and names no material. ![The game's whole screen: a sheet of paper on a wooden table with a blue watercolour wash, a red ketchup zigzag and a lit birthday candle on it, and on the left the drawer tabs with the Garden drawer open.]() **In the game.** The released game's screen, with a wash of watercolour, a ketchup zigzag and a lit birthday candle on the paper, and the drawers of tools beside it. Everything a child does lands on that one sheet. ![In the game: on the right the paper has burnt away to the wooden table; its flames are held at the edge of a band of wet paper, faint grey patches, where a black marker dot has opened into a blue rim round an orange-brown middle.]() **In the game.** The scene at the top of this page, in the released game, 40 s after the match: the fire has burnt the right of the sheet away and is held at the band of poured water, which it has to boil dry before it can burn on. Given long enough it does get through. In the band, a black marker dot has opened into a blue rim round an orange-brown middle. ### Plain text Every chapter's headings and captions tell the story on their own. Read only those and you know what's special. ### \+ Under the hood The engineer's layer: the idea behind each rule, real units and grid sizes, the shortcuts we take and how a test holds each result. ### The game's own rule The game's own rule A live demo running the game's real rule and constants, only on a smaller grid. Illustration marks a sketch of the idea. ### next update next update Built and tested, coming in the next update. Everything without this badge is in the game you can play today. ## Nothing in the code says a football can blow out a candle In most games, a programmer decides what happens when two things meet: "if the ball touches the candle, put the flame out". Professor Oops almost never works that way. A rolling ball only pushes the air in front of it. A candle only checks how fast the air round its flame is moving. Neither knows the other exists. Roll the ball past fast enough and the flame goes out, because they share the air. The same goes for heat, water, what is dissolved in the water, noise and shaking. Each tool writes into a few shared layers, and each thing on the page reacts to those layers by its own numbers. [Built for surprises]() maps them all and lets you follow each one's connections. Scientists call this emergence. The behaviour comes from parts that share one world, with no list of special cases behind it. It is also why the game can answer questions nobody wrote into it. [Under the hood](<#hood-emergence>) Nothing in the code says a football can blow out a candle Under the hood ### Nothing in the code says a football can blow out a candle Systems never call each other. They write into shared layers: per-cell fields such as heat, wetness and acid, the air and the grids animals sense, and a few shared ways in for pressing, rubbing and knocks. A TypeScript AST scan with the type checker over the whole simulation found 689 read and write links in the released game, between 33 systems and 55 layers, at 5,539 places in the code. In 882 of the 1,056 ordered pairs of systems, one writes something the other reads. A second scan looked for any rule that tests one named material against another. Across the 5,356 pairs of substances in the released game it found none. Chemistry between dissolved substances is written once, as a table \(vinegar fizzes on soda through a rule about acid and soda\), and the tests check the other way too: an automated test fails if the speaker's code names the salt it moves. The full map, the counts and the exceptions: [Built for surprises]() Shared: wind ### Roll a football fast past a lit candle The flame goes out from the ball's wind, with no rule about balls and candles \(pinned by a test\). [Air that really moves]() Shared: CO₂ in the air ### Fizz vinegar on baking soda near a candle The heavy gas creeps along the paper and puts the candle out: one 26 cells away goes out, one 84 cells away doesn't \(pinned by a test\). [Chemistry and pH]() Shared: carbonate \(a base\) ### Burn a patch, then paint red cabbage juice over it The juice turns blue in a thin ring round the burn and stays purple on clean paper, because burning leaves carbonate in the ash and the indicator reads pH \(pinned by a test\). [Heat and fire]() Shared: acid ### Clip a battery across salty water on cabbage paper The water by the plus clip turns pink \(pinned by a test\). [Electricity]() Shared: wet \+ water ### Paint water across the path of a fire A match won't light it, and the front stalls until the water has gone \(pinned by a test\). [Water in paper]() ## 97 materials, from ketchup to sand, and not one rule written for a pair of them Every figure here comes from the released game's code, a test or a recorded measurement, and the chapters say which. 97 Materials in the released game, from ketchup and honey to sand and paint, each described by numbers in one shared table. 0 Rules that name two substances, across 5,356 pairs of them. Found by a scan of the code, then each candidate read by hand. 55 layers Shared layers, such as heat, wetness, wind and noise, that 33 systems read and write through 689 links. 882 of 1,056 Ordered pairs of systems where one writes something the other reads. Nobody wired those pairs; the layers do. 2,614 Tests in 270 files at the release, with 8,933 assertions. Many of them step the real engine on a real page. 7 kernels WebAssembly copies of the busiest loops. Five are tested to the last bit against their readable JavaScript twins. 2.9× The most the paper kernel sped up its own simulation, 1.8 to 2.9× across scenes, timed on a desktop when it was ported. No tablet was timed. 4.6× Less fire work on a warm dough page where most of the tiles have settled and sleep, with the result identical to the bit. ## Sixteen chapters, from water and fire to animals and speed, all on the same sheet Each chapter takes one part of the world on the paper: what a child sees, what is really computed, how it links to the rest, and where we simplify on purpose. Most have live demos running the game's own rules. ![Painted illustration of the painter crouching by an oven, watching a crayon drawing toast golden inside, with an ice-cube tray and a lemon.]() Start here · Built for surprises ### [A ball blows out a candle, though no line of code says it can]() How every system writes into a few shared layers and reacts by its own numbers, and the program that read the code to count the links. 689 links · 55 layers · 0 pair rules. ### The world on the page Thirteen systems, each with its own rules, all on the same sheet. ![Painted illustration of paper strips and a coffee filter in glasses of water, where black marker dots have spread into blue, pink and yellow bands, watched by the painter.]() Water in paper ### [Water creeps through the paper and takes the colour with it]() Marker rings, darker drying edges, tea stains and salt painting, from water moving between neighbouring specks. salt-crust water kept to 1e-6 over 600 solves. ![Painted illustration of the painter brushing a rainbow watercolour that bleeds into wet paper, with crayons, markers, a paint box and a child's rainbow drawing.]() Pencil, crayon and paper ### [Every line remembers what drew it]() A smudge, a wash and a later pencil each read a different store, so pencil smudges under the hand and stays under water. smudges when dry · holds under water. ![Painted illustration of the painter shaking a jar, beside a jar of golden oil floating on blue water, a jar of creamy mayonnaise, an egg yolk and mustard.]() Runny, sticky and oily ### [Ketchup stands, honey runs and oil floats, with no code for any one liquid]() Two numbers decide whether a sauce holds its bead; three questions decide what floats; no file that moves liquid names one. 3 layers a cell · 0 liquids named in code. ![Painted illustration of the painter on a sunny windowsill lifting a leaf off faded blue paper, where the leaf, a key and a star left darker shapes.]() How colours mix ### [Colours mix like paint because the game stores the light they soak up]() Three numbers per spot, so stirred paint lands between its colours and washes laid over each other go darker. A = −ln c · drawn as e⁻ᴬ. ![Painted illustration of the painter pouring purple red cabbage juice into a row of glasses that go from pink through purple and blue to green, with a lemon and baking soda.]() Chemistry and pH ### [Every spot of paper knows how sour it is]() Twelve dissolved things per spot, eleven reaction rules, and red cabbage juice to show the pH. 12 dissolved things · 11 reaction rules. ![Painted illustration of the painter pointing at a golden-brown heart and star that appeared on paper after ironing, with an iron, half a lemon and a cotton bud.]() Heat and fire ### [Every speck has a temperature, and fire finds its own speed]() Irons, candles, lenses and batteries write one thermometer. No line of code sets how fast fire spreads. paper lights at 230 °C · front 1.85 cells/s. ![Painted illustration of the painter blowing soap bubbles over a toothpaste stripe, a sponge, soap suds, a spray bottle, cotton buds and a hair dryer.]() Air that really moves ### [One invisible wind blows over the whole page]() Fans, hair dryers, footballs and hot cups push the same air, and flour, smoke, smells and flames answer it. 64 × 48 air cells · multigrid solve. ![Painted illustration of the painter stroking his beard as he looks at a light bulb in his hand, a magnifying glass and a crayon on the table.]() Electricity ### [The current finds its own way through whatever you draw]() Real volts, ohms and amps on every speck, through copper, pencil and salty water, with nothing telling it how the wires join. one bulb 0.273 A · exact solve 0.272 A. ![Painted illustration of the painter pushing a toy car through blue paint, leaving tyre tracks, beside a monster truck, a beach ball, a football and a marble.]() Things that push things ### [A football knocks a mug over; a marble only rattles it]() One bump rule from weight, size and height, one press a dozen systems feel, and one downhill when the tablet tilts. J = −\(1\+e\)·vₙ / \(1/mₐ \+ 1/m\_b\). ![Painted illustration of the painter studying a splash of blue ink through a magnifying glass, with a hammer, a squashed marker, a scraper, a ruler, an iron and a bank card.]() Light and shadow ### [Ketchup, puddles and pencil dents stand off the page, and one light shows every bump]() Every spot has a height, so paint, dents and puddles are lit alike, and a still magnifying glass can burn. a height on every spot · one key light. ![Salt on the paper gathered into a symmetrical lacy figure around the speaker held in the centre]() Sound and shaking ### [A speaker shakes the paper, and salt draws the figure by itself]() The speaker only shakes the sheet; salt and flour move by their own grain rule. Every sound effect is made by code as it plays. hundreds of vibration shapes · 0 recorded sounds. ![Painted illustration of the painter in oven gloves sniffing a golden loaf, with a ball of dough, a rolling pin, a bowl of yeast and a pretzel.]() Dough, mould and time ### [Dough rises, mould spreads and cress sprouts, and a button skips three days ahead]() Yeast, gluten and salt in every speck of dough, and a three-day wait worked out instead of played. 3 days worked out, not played. ![Painted illustration of the painter watching a line of ants march to a drop of honey through a magnifying glass, with a snail, sprouting cress and a watering can.]() Animals with their own minds ### [A cat, a puppy, ants, flies, a pigeon and a snail notice the world for themselves]() They hear, feel and smell shared layers, follow scent trails a child can break, and are never hurt. 3 sense layers · 488 harm checks. ### Engineering How it stays fast on a cheap tablet, and how it stays right. ![Painted illustration of a tablet and a phone on a yellow sheet with a ketchup zigzag, both screens showing paint splats, milk swirls and a crayon house, the painter smiling at them.]() Fast on a cheap tablet ### [The paint under your child's finger keeps moving]() A Web Worker, WebAssembly kernels, tiles that sleep and a scheduler that serves the hand first. 7 kernels · the hand served first. ![Painted illustration of a painter's worktable with sketches pinned up, paint pots, crayons, a sketchbook, a laptop, a ketchup bottle, red cabbage juice and a beret on the chair.]() How we keep it right ### [Thousands of automatic tests do what children do]() Tests that play like children, fast loops held to readable twins, and promises to families written as checks. 2,614 tests · 0 any under strict. ## The game keeps what a child can see and test, and drops the rest of the physics on purpose A tablet can't compute the real world, and a child doesn't need it to. The craft is choosing what to keep: the effect a child can see and test, at a cost a cheap device can carry. Here are six of the shortcuts, each explained in its chapter. **In real life.** pH comes from the balance of ions in each drop of water **In the game.** A rough reading from the amounts in a spot, anchored on vinegar's real pH; red cabbage's colour is looked up in a table blended from a few hand-picked colours **Why that's enough.** The colours come in the order the printed charts give, at one lookup per spot. [Chemistry and pH]() **In real life.** The dyes in an ink separate by their chemistry **In the game.** Each of a black marker's three dyes rides the water at its own speed, typed in like the Rf values of a school experiment **Why that's enough.** The rings come out of the water's own movement, in the right order. [Water in paper]() **In real life.** Air is close to incompressible **In the game.** Only part of the pressure correction each tick, on purpose **Why that's enough.** Seen from above, a fan is a source of air and a fire a sink; a full solve made gusts weaker. Swirls are weaker than real ones. [Air that really moves]() **In real life.** An ant's scent trail lasts about 47 minutes **In the game.** It fades within a minute or two, dozens of times faster **Why that's enough.** A trail has to clear within one play session, so a child can watch it go. [Animals with their own minds]() **In real life.** Sound is a pressure wave that travels and echoes **In the game.** No sound waves are computed. The speaker writes a steady shake map, a sum of a few hundred vibration shapes **Why that's enough.** Salt finds the still lines all the same, on a full page, on a tablet. [Sound and shaking]() **In real life.** A mould colony spreads faster when it is warm and well fed **In the game.** Its size is a formula of its age, with a cap **Why that's enough.** Three days cost one sum, and it slows under a child's eyes. A warm room and a cold one give the same size. [Dough, mould and time]() ## 179 sources on play, real science and selling to children, each labelled by what it really did Four pages list every source we drew on, from fluid solvers and forensic drop stains to real ants and the rules on selling to children. Each one is labelled by what it really did: applied, shaped a rule of our own, or found later and consistent. We have run no learning study, and we don't claim one. [The research behind it]() brings them together. ![Painted illustration of the painter blowing coloured bubbles over a bowl through a straw and holding up paper printed with lacy blue and pink rings.]() The science of simulating ### [Built on the research, cut down to what a child can see]() Two methods followed by name, the rest cut down to fit a tablet, and the clever papers we turned down. 56 sources. ![Painted illustration of the painter with a clipboard at a teacher's desk with a binder, red cabbage juice, a magnifying glass, an ice-cube tray, cress and a tablet.]() Real facts, real animals ### [Real science sets the direction, play sets the pace]() Ants that steer by a measured rule, paper that lights near real paper's temperature, and where we bend the numbers. 57 sources traced to the code. ![Painted illustration of the painter finger-painting a big sheet covered in hand prints, paint splats, a toothpaste squiggle, glitter and a cracked egg.]() How children learn through play ### [A world that answers back, and nobody keeping score]() What research says about surprise and self-led play, where the game fits it, and where it pushes back. 0 goals, scores or ways to fail. ![Painted illustration of a wooden toolbox tied with a red ribbon next to a single coin on a yellow sheet with a ketchup zigzag, the painter reading a book beside it.]() Designed with respect for children ### [We read the rules on selling to children, then built to them]() No ads, nothing locked in play, a grown-ups' sum, at most three asks, one purchase. 0 ad or analytics libraries.