So a friend wanted me to try out the reverse-puzzling riddle he created. It consisted of a 4x4 grid with a digit in each cell and a single closed loop drawn along the edges of its cells. Also some of the cells were highlighted in green.
You were supposed to answer the following questions:
What does it mean for a cell to be green?
Which two types of puzzles inspired this one?
But to be honest, answering those questions was way too trivial given the complete grid, so I suggested to remove the digits and the loop from the grid and see if people would still be able to answer both questions. They were not, because we forgot to mention that the loop was somehow involved.
Given that story and the image, your actual task is to recreate the initial grid by filling in the correct digits and the correct loop!
If your assumptions about the rules are correct, this solution will be unique.
Comments with questions, solutions and/or deductions are highly appreciated.