Logic Masters Deutschland e.V.

This puzzle is a sequel to the original Fog and Phantoms pack, and continues its story. If you want to follow the story, I recommend playing those puzzles first.

11 years later...

Your father’s always been a strange one. Who’s heard of a navigator who won’t set foot on a ship? Still, he makes a tidy living selling the charts he draws from memory. He won’t touch a lock, so tonight you’re stuck at home, waiting to unbar the door when he returns. You don’t mind. It gives you a chance to open up his trunk, and look through the relics of the life he left. You pull out the false bottom he doesn’t think you know about, palm his compass, and unroll the old map he refuses to sell. The O’dusku Strait. A perilous tangle of reefs. Your heart hammers as you set the compass upon the parchment. It’s doing it again. Wandering this way and that, but never pointing north. You run the brass across the parchment and it traces out the edges of… something. Tonight you’re going to figure out what.

Rules

Normal sudoku rules apply.

Phantoms: Some clues are phantoms and may only reveal themselves as the grid is shaded, for this reason, you may only shade the grid once allowed to by the other rules.

Seas and Reefs: Use two colors to shade the grid. The digits 6-9 will represent reefs, while the digits 1-5 will represent navigable water. Within each 3x3 box, The reef cells will form a single orthogonally connected group, as will the water cells. You may only shade a cell once you have determined whether it is reef or water.

Difference Arcs: The digit placed in a cell containing a pair of spoked arcs will be equal to the difference between the values of those arcs. Each arc has a value equal to the sum of the neighboring cells that their spokes point towards.

For example, in the image below, the sum of the cells marked with an A will differ from the cell marked with a B by C.

Dynamic Fog of War: Most of the grid is covered in fog. Placing a correct digit in a cell will always clear the fog from that cell, and may clear fog elsewhere in the grid.

Note: Phantoms are tricksy, and will cause some clues to temporarily disappear when the pen tool is open. Don't worry, the clues will return when the tool is closed, and any markings you have done in the meantime will remain.

Click here to play, or click here for a version without the cosmetic borders. I definitely went overboard on the aesthetics for this one, so if you find they're interfering with your solving experience, give the second link a go; you won't miss out on any story. Either way, I generally find that shading with darker colors shows clues more clearly.

This puzzle wouldn't have been possible without a great deal of help. I want to thank ChinStrap for help with troubleshooting, and Calvinball, ThePedallingPianist, and SennyK, for their invaluable help with testing. I'd also like to thank so many of you for encouraging me to continue the series after playing the first puzzles. Thanks folks!