Medium boards expect the classic intermediate technique: confinement. When all of a region's remaining cells sit in one row, that row's stars are spoken for — and every cell of the row outside the region can be marked. Spotting those squeezes quickly is what separates a medium solver from a beginner.
This is the everyday difficulty for regular players: enough resistance to be satisfying, never a grind. If a board stalls, the strategy guide covers the counting arguments that unlock most medium positions.