Easy — logic-grid deduction puzzle
Edith, Walter, Ruby and Sylvia race the wind to bring supplies to a lighthouse before dark.
The lighthouse keeper has run short of supplies and needs them before dark. Edith, Walter, Ruby and Sylvia meet at the harbor and load the little boat while sea spray blows over the wall. They split the day between them. Each one takes a watch, carries one supply up to the tower, and raises one signal flag so the keeper can see how the trip is going. The crossing is short, but the wind is picking up, and it could turn into a long day.
Read the clues, rule out what cannot be, and prove what must be. Every GRIDIGMA puzzle is verified by a solver that shows the reasoning behind each step, so a solution is never a guess.
Logic grid puzzles: how to solve them, with a worked example