• ✓Idea: a child should DO adding and subtracting with a finger before meeting numerals
• ✓Not a multiple choice: the working board starts as pattern A and the child does the operation
• ✓One tap at a time, so the picture changes step by step
• ✓A wrong tap fills nothing and gives the real reason ("that cell isn't in B")
• ✓Teaches the overlap: in A + B a cell in both still only counts once
• ✓Two boards: a 3×3 grid and a seven-hex flower
• ✓Every puzzle is generated fresh, and only kept when the operation actually does something
• ✓The reveal card puts it in numbers (5 cells + 3 cells = 6, because 2 overlapped)
• ✓Add an intersection sign (A AND B) as a third operationplanned

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