Wednesday, 17 April 2024

Menderbug

Today's genre goes by the catchy name Cross Border Parity Loop. It was invented by @puzzlecraig and first introduced at last year's World Puzzle Championship. The full ruleset is a little more general than what we're using here (allowing for question mark clues and internal borders), but let's keep it simple for now.

Rules: Draw a single, non-intersecting loop that has two states, which are white and black. Whenever the loop crosses a region border (and only then), it changes state from white to black or from black to white. A black circled clue provides the number of cells in each area that the loop traverses in the black state, and a white circled clue provides the number of cells in each area that the loop traverses in the white state.

Notation tips:
You can either use the auxiliary X and O markings from the pre-selected mode, or you can switch to Surface mode and shade cells in two different colours to keep track of the loop's state (e.g. if you want to use X and O to mark empty and visited cells instead). However, the answer checker here only cares about the loop itself.

Score a Speedy Sloth 🦥 by solving the puzzle in 2:30 or less!
Collect a Quick Crab 🦀 by completing the puzzle in 5:00 or less!
Finish the puzzle in your own time to become the proud owner of a Black-and-White Crossbill 🐦!

Example (Penpa+): https://tinyurl.com/2cbtxchn
Puzzle (Penpa+): https://tinyurl.com/2xhe2qlo