Think of a number. Any number between 1 and 1000.

Don't write it down. Don't tell anyone. Just hold it in your head.

If you just came back — you saw it happen. You answered a few questions, and the computer landed on your number. Not by luck. Every time. For any number you could have picked.

There's something quietly unsettling about that. You were certain you had control. You chose the number. You gave the hints. And yet it felt like the game was over before it started.

The Trick Isn't What You Think

It's not a trick, actually. No hidden camera. No reading your mouse movements. No AI trying to predict human behavior.

What the computer is doing is something much older and stranger: it eliminates half the remaining possibilities with every single guess.

You start with 1000 possible numbers. After one question, 500 are gone. After two, 500 become 250. Then 125. Then 63. Then 32. Then 16. Then 8. Then 4. Then 2. Then 1.

Ten steps. Any number. Every time.

It works because the space of possibilities — no matter how large — collapses exponentially when you cut it in half repeatedly. 2 to the power of 10 is 1,024. That's more than 1,000, which is why 10 questions are always enough.

This is called binary search. It's one of the oldest ideas in computer science, and it shows up everywhere — in databases, in dictionary lookups, in version control, in how your phone's contacts list finds a name in milliseconds.

But the reason I like it as a party trick is that it reveals something about intuition versus math. When you're choosing a number, 1000 feels like a lot. A machine guessing it in 10 steps feels like magic. The reality is neither: it's just that exponential decay is faster than human intuition expects.

Why I Built This

I build software for a living — mostly EU e-commerce and SaaS systems where the hard problems are in the complexity: tax rules for 35 countries, order automation pipelines, AI integrations that have to be fast and cheap at scale.

But the ideas underneath all of that are usually simple. Binary search is one of them. I built this game because it's the cleanest demonstration I know of how a small, elegant rule can feel impossible from the outside and obvious once you see it.

If you haven't played yet, go try it. Pick a difficult number. See how many guesses it takes.

It'll be fewer than you expect.