Logic Masters Deutschland e.V.

To Christmas 2024 some eager puzzlefriends have again arranged a group in which everybody had to make anonymously a puzzle for someone else. These puzzles are now presented one after the other here in the portal.

After an inspiring visit to the North Pole, the two puffins Knusi and Schmusi return to the South Pole, as refugees from the Danish fishing industry, and enthusiastically set about starting their own puzzle workshop. They already know exactly who the first puzzle recipient will be: the brave pin7guin Dina.
Schmusi says: I know that she loves to let off steam as a figure skater. How about if we build her a super-slippery roller coaster on an 11x11 grid, where each row and column must contain the numbers 1-9 once each, as well as two blacked-out cells each?
Knusi replies: I had thought of something like that too: the roller coaster must visit all the fields in a single loop, but the 1s and 9s are treated specially. The 9s can also be optionally blacked out — and can therefore only be visited by the loop if they are not blacked out. The 1s, however, must always be used as crossing points at those points where they are surrounded by 4 unblackened cells. So the loop must form a big plus sign in those spots. Elsewhere, however, the loop must not visit a cell more than once.
Schmusi: Oh yes! In the margin we can give the route sums in the correct order, at least in part... An asterisk would then stand for none, one, or several further clues, and a '?' for any digit (but, as is also usual at the North Pole, without a 'leading zero').
Before Knusi can speak, Schmusi adds: ...And to emphasize the 9s and 1s even further, let's say that the sandwich sum that applies to each row and column is also given. Knusi: Can you tell me again what a sandwich sum is? And where we want to write it down? Always at the very edge? Schmusi: The sandwich sum is simply the sum of the numbers that are between 1 and 9 in the relevant column or row. And I think we can insert it anywhere we want, although it can also be swallowed up by an asterisk or question mark constellation. Claudia can certainly manage that. Knusi: That's great! And look: there she squats already, lacing up her skates. Both puffins waddle enthusiastically towards their first customer, with the finished puzzle tucked under a fin.