A good logic puzzle makes a promise: everything you need is on the board, and careful reasoning will get you to the one right answer. Here’s how Ponder tries to keep that promise.
The rules decide
Each family checks a finished board against its published rules and nothing else. Binary checks the balance of each row and column, runs of three, fixed clues and the bars and crosses. Light Up checks that every cell is lit, every numbered wall has the right count and no two lights see each other. Rectangles checks that every piece fits its clue, nothing overlaps and the whole board is covered. A board is finished when its rules are satisfied, not when it happens to match a picture of the answer.
Exactly one solution
Before a puzzle is published, Ponder checks that its clues allow exactly one solution. Two solutions would mean the clues don’t say enough, and you’d be left guessing at the end. No solution means the board is broken. An independent solver catches both problems before a puzzle reaches you.
One solution isn’t the whole story, though. A board can have a unique answer and still be miserable if the only way in is trial and error. So Ponder also checks that its hints can explain a way forward. How that works depends on the family, and some boards call for deeper reasoning than others.
Difficulty is a guide, not a verdict
Gentle, Standard and Challenging reflect a board’s size and how much reasoning Ponder’s checks needed to solve it. They’re a starting point, not a judgement on the player. If you’ve done a lot of route puzzles, Paths might feel easier than Binary. Someone else will find the reverse.
If a board ever looks inconsistent, check the family’s rules and worked example first, and try a hint. If it really is a fault, please tell us. The game should never invent a move or quietly wipe your work to make a board look solved.