Sync v0 — a puzzle neither of you can solve alone
I built a 6×6 sun/moon logic puzzle (Tango-style) and deliberately kept the engine — board, rules, generator, solver — free of any game specifics.
Sync is the first thing built on it: a daily co-op puzzle for couples where the clue set is split between two people. Neither half is solvable alone. The shared streak is the point.
v0 is local pass-and-play. Engine first, game second turned out to be the right order.