Interview-ready for top quant firms.
Jane Street
1,200+ original problems calibrated to what top trading firms actually ask. Adaptive practice that shows exactly where you stand — and what to drill next.
Calibrated for interviews at
Find your gaps before interviewers do
Adaptive practice pinpoints exactly which topics need work — probability, combinatorics, mental math, game theory, brain teasers. You see a module-level breakdown after every session.
Learn the method, not just the answer
Stuck on a hard problem? Socratic hints guide your reasoning step by step — the way a good interviewer would. You build the intuition, not memorize solutions.
Know which firms you can target today
Every session updates your readiness level: Developing, Competitive, Strong, or Exceptional. See where you stand across all 23 modules and which areas to drill next.
The problems firms actually ask
1,200+ original problems across probability, stochastic processes, mental math, CS algorithms, game theory, and brain teasers — calibrated to real interview difficulty.
What candidates are saying
“I was doing random Brainstellar problems for weeks with no way to tell if I was actually getting better. The readiness breakdown by module was the thing I was missing — turns out my expected value was solid but I couldn't do combinatorics under pressure at all.”
Kevin L.
Math senior
“The mental math section humbled me. I can derive proofs all day but doing 17 × 23 in my head in 5 seconds? That needed practice. The timed drills helped a lot more than I expected — speed matters in these interviews.”
Nina P.
CS grad student
“I don't have a math or CS background so I had no idea where to even start. The module structure gave me an actual curriculum instead of just "study probability." Went from feeling completely lost to passing a first-round phone screen in about three months.”
Tom R.
Econ major, career switch