HOW WE STARTED

Built in 14 days because the existing IQ tests were terrible.

Core Brain wasn't supposed to be a business. It started as a weekend frustration with how broken online IQ testing had become.

The problem

I'd been curious about my own IQ — properly, not "8th-grade-teacher-said-I-was-smart" curious. I started looking around at what was available online. The landscape was bleak:

The clickbait tier. Fifty test sites that ask you 5 to 10 multiple-choice questions and then dump a "Your IQ is 137!" screen designed to make you share it on Facebook. No methodology disclosure. No confidence interval. No way to verify the number means anything.

The lead-magnet tier. Sites that let you take a 20-question test, then lock the result behind a $49 or $99 paywall after capturing your email. Designed to push you into a refund-process you'll never use.

The legit-but-painful tier. Real psychometric communities (r/cognitiveTesting, cognitivemetrics.com, RIOT IQ) running real tests with real calibration — but the UX requires a Reddit account, a willingness to dig through whitepapers, and tolerance for tests that take 45+ minutes.

There was no middle ground. So I built one.

"An IQ test should give you a real number with an honest confidence interval — and it should take twenty minutes, not three hours."

The build

I gave myself two weeks. The constraint was: ship something genuinely calibrated, not a quiz dressed up as a test. The core technical requirement was real Item Response Theory scoring — 3PL Bayesian MAP estimation, the same statistical framework as the WAIS-IV.

Days 1-3

Built the IRT 3PL scoring engine from scratch in TypeScript. Newton-Raphson MAP estimator, Fisher information for SEM, 95% confidence interval computation.

Days 4-7

Calibrated the item bank — 200 items across 5 difficulty tiers, each with discrimination/difficulty/guessing parameters derived deterministically from item content.

Days 8-10

Built the UI. Six cognitive axes, stratified sampling, per-axis sub-theta estimation. Six-axis radar chart, bell curve overlay, downloadable PDF certificate.

Days 11-12

Stripe payment integration. Single $15 unlock, no subscriptions. Server-side verification of every paymentIntent.

Days 13-14

SEO foundation. Domain on Vercel. 94 programmatic landing pages built from MBTI types, career averages, IQ score explanations, age cohorts.

Day 14

Live at corebrain.app.

What's next

The IQ test itself is feature-complete. The next chapter is the Brain Training dashboard — a growing suite of calibrated cognitive exercises (reaction time, working memory, attention, fluid reasoning, spatial rotation) with a real progress dashboard. Access is private while invites are being opened.

If you want to follow along: the calibrated test is at the bottom of every page. Take it. Tell me what you think.

Take the test →