Combine numerical deductions with crossing and connectedness checks. Compare an apparently complete board with an actual connected solution, and identify the route a component still needs.
What range can the displayed capacity deduction establish for route B–G?
Written explanation
Island B needs 3 individual bridges. Its routes currently allow 0 to 4 in total. Holding the other routes within their limits restricts B–G to 1 or 2; B–A to 1 or 2. A domain “1 or 2” proves a connection but does not yet choose single or double.
This question begins at the displayed checkpoint. The full practice link starts at the board’s opening position.
TRY IT 2 · bridges-remaining-2
What can you justify?
What range can the displayed remaining deduction establish for route G–H?
Written explanation
Island H needs 2 individual bridges. Its routes currently allow 1 to 2 in total. Holding the other routes within their limits restricts G–H to 2. A domain “1 or 2” proves a connection but does not yet choose single or double.
This question begins at the displayed checkpoint. The full practice link starts at the board’s opening position.
TRY IT 4 · bridges-connectivity-2
What can you justify?
Consider connectivity alone: removing G–H splits the graph of remaining possible routes. Which range does this connectivity test establish for that route, without using additional island-count deductions?
Written explanation
Removing G–H would split the graph of all still-possible routes. Every island must belong to one network, so G–H must carry at least one bridge. This does not by itself decide between one and two.
This question begins at the displayed checkpoint. The full practice link starts at the board’s opening position.
Apply the ideas to a complete board
These are fixed original studies, not new daily puzzles. The three study links below and this collection’s printable pack use identical starting positions. Their checked solution routes are included on each practice page. A collection’s technique drills may also appear in its lessons.
13 steps in the included checked route. Try the board first, then compare the reasoning.
The order uses a repeatable rule trace, not a human difficulty score. A shorter trace is not guaranteed to feel easier. Lights studies are ordered by their construction plans.
Playfield Arcade · Updated 3 October 2026 · AI-assisted writing and code; examples checked against explicit constraints. Our method · Report a correction