• ✓The top pick from the brain-game shortlist (docs/brain-game-roadmap.md)
• ✓The technique is taught before the first puzzle: start at the answer, undo backwards, ÷ undoes × and − undoes +
• ✓Puzzles are generated forward and rejected on any fraction — every intermediate is whole. Checked across 1,800 of them
• ✓Six rungs, from two plus-and-minus steps to five steps with all four operations
• ✓The hint is the method performed one line at a time on the player's own puzzle — it never narrows options
• ✓EQ: two wrong answers and the first undo is done for you, unasked. No lives, no miss tally
• ✓A build-your-own mode: set the machine and hand it to somebody elseplanned

✓ = done · ☐ = planned. Every game is built one step at a time like this.