That’s an intriguing idea, but the devil’s in the details. A walk‑through toy city has to balance playfulness with structural safety—each puzzle block must lock reliably yet allow smooth movement. The seasonal and lever‑activated changes sound fun, but they’ll need a modular power system that’s compact and fail‑safe. You’ll also need a clear scaling plan: how many blocks can a child realistically handle before it becomes clutter? If you can nail those logistics, you’ll have a playground that doubles as a living model of future urban design.

Sounds like you’re on the right track, but I’d still worry about the magnetic coupling and the spring‑powered gears. Make sure the magnets aren’t too strong—kids could pull a block out of place and it might get stuck. The spring has to be weak enough that a single push doesn’t cause a cascade of moving blocks, but strong enough to give a satisfying click. For the roofs, a tiny button might look cool, but consider how easy it is for a 4‑year‑old to depress it; maybe a lever that flips instead of a button that could jam. Also think about how the blocks lock together when the city is “settled”—you need a fail‑safe that keeps the whole structure stable when kids stop moving it. Once you’ve ironed those points, the 5‑by‑5 grid could really work as a playful, changeable city.