Pick an act, then a region. Each region page replays every board: press Step and watch the walls appear, with the reason for each one written out - which clue, which rule, why nothing else fits. No guessing: a step is drawn only when the clues force it.
How to read a replay.1 clue settles an edge on its own. 2 clues means two clues read together - every arrangement satisfying both agrees on that edge. 3 clues means three at once. Only when all of that is exhausted does a board fall back to a what-if. Act I needs none.