RECALL
A practice tool for blindfolded Rubik's cube solvers that keeps the next scramble ready and makes every failed attempt record why it failed.
Blindfolded practice fails in patterns, and a plain timer forgets them. I hold the Nepali national record in 4×4 blindfolded, set at Nepali Nationals 2019, and the categories of failure in Recall come from my own practice, not from interviews.
Two decisions shape it. The loop is always ready: after a solve, the next scramble appears without a 'next' tap. A failed attempt goes the other way: before moving on, you pick one of six reasons it failed, while you still remember.
Each attempt moves through clear steps: scramble ready, memorising, solving, grading, and a reason if it failed. Memorisation and execution are timed separately, and the time spent putting on the blindfold isn't counted. Each solve saves the details of its scramble as you saw it, so history stays accurate. There is a separate log for multi-blind attempts.
Scrambles can target a difficulty, such as the number of edge and corner targets or whether parity appears. If no close enough scramble turns up, the tool says the match wasn't exact. It also guards against a double click saving one attempt twice, and against an older scramble replacing a newer one. It runs in the browser and can be installed as an app.
The limit: if saving an attempt or generating a scramble fails, the screen doesn't say so; the only way out is to skip. And whether it makes me a better solver is not measured.
Next I would show a clear 'not saved' state, run and extend the tests for rapid input and reloading mid-attempt, and look at which failure reasons come up most over a few weeks of practice.