Tools
Working instruments for the kind of arithmetic that usually wants a spreadsheet, a consultant, or both. They run inside this site, they cost nothing, and they ask for nothing.
What these are
Each one is a page that does a single job and leaves its working on the screen. There is no account to make, no trial, no cookie banner and no analytics, because there is nothing here that watches you. Everything you type is computed in your own browser and never leaves it.
Free, and free of accounts
No sign up, no trial, nothing to buy. A static page costs nothing to serve, so there is no subscription behind any of this and no reason to ever put one there.
Nothing is tracked
No analytics, no cookies, no database, no server. Once the fonts have arrived there is no network call left for the page to make.
Computed in your own browser
Your figures stay in the page you typed them into. After it has loaded once, it keeps working without a connection.
Every constant carries its source
Where a tool holds a rate, a threshold or an emission factor, it prints the publisher, the value and the date that value was read.
A missing number is named, not invented
Where a tool cannot know a figure it says which figure is missing and who holds it, and refuses to close the gap with a plausible guess.
The instruments
Carbon and compliance
CBAM cost and data gap
For importers bringing steel, aluminium, cement, fertiliser, hydrogen or electricity into the EU. Says whether you cross the fifty tonne threshold, prints the certificate cost one arithmetic step at a time, and lists every emissions figure you are still missing together with the supplier who holds it.
Being built: a carbon inventory for small manufacturers, a household footprint that prints its uncertainty beside every line, and an emission factor dictionary where each figure carries the document it came from.
Finance and analysis
Analyst desk
For students, analysts and founders sizing something before a meeting. A discounted cash flow that shows how much of the value is the perpetuity behind the forecast, two market sizings with the gap between them left visible, a runway that names the month the money ends, and a converter that refuses a conversion it cannot make safely.
Being built: an invoice and small trader tool for freelancing from Germany, and a ledger of climate and energy series that keeps the revision history instead of overwriting it.
Living and working in Germany
Werkstudent
For international students working alongside a degree. What actually arrives in your account from a working student job or a minijob, line by line. The two work limits that students confuse, side by side. What a month costs in six cities. And the arrival paperwork in the order it has to happen. This one speaks English, Turkish and German all the way down.
Being built: a Turkey to Germany moving guide in the order things actually happen, and a decoder for a German electricity or gas bill.
The essays
Explorable Economics is not an instrument, and it is kept apart for that reason. You bring nothing to it. The model sitting in the middle of each essay is there so the argument can be checked rather than believed, and every essay ends by saying what its model cannot tell you.
Explorable Economics
Drag the supply and demand curves and find that the statute does not decide who bears a tax. Run a used car market until the good cars withdraw. Hold a tournament between strategies, then let the winners reproduce. Move a discount rate and watch a catastrophe a century out turn into a rounding error.
Who actually pays a tax
Essay oneTax incidence. Who hands the money to the state turns out not to matter; elasticity decides.
The market for lemons
Essay twoAdverse selection. What one side knows and the other does not, until the good cars leave the market.
The evolution of cooperation
Essay threeThe repeated prisoner's dilemma, a round robin between strategies, and then a population that reproduces.
Why the future is cheap
Essay fourDiscounting. One rate, chosen quietly, decides whether a distant catastrophe is worth preventing today.
The simulations
SIMEA is my research programme, and a written framework is easy to agree with and hard to test. These five agent based models sit beside it so that the claims can be run rather than believed. They are the same kind of page as the essays: nothing to bring, a model in the middle, and a closing section on what the model cannot show.
The SIMEA simulations
Watch a mild preference settle into a severely separated city. Set a recommender loose on a population and run the same population beside it with a neutral feed, with the influence gradient, the autonomy threshold and the entropy of the choice environment defined on screen and measured while it happens. Hold a contagion fixed and change the shape of the network under it. Jam a ring road that has nothing blocking it. Drop grains on a pile until it tells you that the size of the next event cannot be forecast.
Segregation without a bigot
Simulation oneSchelling's board. Nobody on it is prejudiced in the way the finished city looks.
The recommender
Simulation twoA feed that chooses what a population sees, run against a counterfactual with a neutral feed.
Diffusion
Simulation threeOne contagion over three network shapes. Structure decides as much as the thing spreading.
The jam
Simulation fourA jam that forms on an empty ring road and travels backwards through the traffic.
The pile
Simulation fiveA pile that holds itself at the edge, where the next grain may bring down a quarter of it.
The games
Some arguments do not survive being read. You can be told that a short rule beats a clever one when the same two people keep meeting, agree with it, and learn nothing. These put the claim in your hands instead.
Game Theory
Six small painted games, each one a situation people are actually in. A neighbour at a fence every season for forty years. Two hunters who can take a stag together or a hare alone. Ten coins and a stranger who can refuse them. A pasture four households share. A number everybody guesses about everybody else. And a coin nobody can afford to be predictable with.
How they are built
Every page here is a single HTML file. No backend, no database, no account system, no analytics of any kind. Nothing you type is sent anywhere because there is nowhere for it to be sent, and that is also why they can stay free: a static file costs nothing to serve.
The shared design and the shared helpers are spliced into each page when it is built, so what ships is still one file you can save, read or copy whole. The bar at the top of this page and the bar on every instrument are generated from the same few lines, which is why they are the same bar.
The source of the site and of every instrument in it is public: github.com/Keremozdemirra.