Medium boards need one more gear than easy: positions where no pattern applies directly, but asking "what happens if this cell stays white?" produces an immediate contradiction. The classic corner patterns and the 2×2 double-pair live in this tier.
The deductions are still local — you never need to reason about the whole board at once — which makes medium the everyday difficulty: satisfying resistance, no grind. If a position stalls, the how-to-play guide walks through every pattern by example.