A diagnostic, not a tutor
You didn't fail algebra.
You failed fractions.
Six years ago.
Every study tool explains the question you just got wrong. Strata goes the other way — it drills backwards through everything holding that question up, and finds the idea that actually broke.
Photo or paste · ~6 questions · no account
01 — Map
Photograph your marked homework, or paste the question. It builds the prerequisite graph beneath the skill you failed — usually forty-odd concepts reaching back to grade four.
02 — Drill
Roughly six questions, twenty seconds each, every one chosen to halve what is still in doubt.
03 — Rebuild
Bottom-up, then it hands back the exact question you failed. Same question.