▦ the deck — a solved region in paint's 8/24 membrane language
…
arrow keys / buttons = wander the lattice (← → wraps the ring · ↑ ↓ walks the axis) · click two rooms = probes A→B, the route threads the doors · regions regenerate identically

← ↑ ↓ → —

solving the region… (~3 s — deterministic: this exact city, every time)