I got this idea from Cameron from the Discord CTC Fan Server.
Create a closed loop by drawing lines to connect cells on the grid. Each cell on the loop can only be visited once before the loop repeats. Consecutive cells in the loop must be one chess Knight's move apart (consecutive cells in the loop are not orthogonally adjacent, but other cells in the loop may or may not be adjacent). The loop must contain exactly one cell from each region of the grid.
To use Penpa to draw a line between two cells that are not orthogonally adjacent, select "Mode: Line" and then "Free" (after "Normal" and "Diagonal"), then click and drag between two cells.
Main puzzle
Penpa link
Here are a couple of smaller ones. I didn't think they were good enough for a separate post so I'm throwing these in here for fun.
Extra Puzzle 4x4
Penpa link
Extra Puzzle 6x6
Solution code:
For the main puzzle, for every row from top to bottom, the column numbers of the cells which the Knight lands on from left to right. (24 digits)
Note: There is an example image here that shows up on the English page but doesn't show up on the German page and I don't know why. Even if I copy the entire thing from the English page and paste it to the German page, the image still doesn't show on the German page. If you are on the German page and you can't see the image, please switch to the English page to see it. Sorry for the inconvenience.
Example: 2 24 3 13
Solution code for extra puzzles (highlight to see)
3 124 23 13 14 236 25 145 146 234
Extra Puzzle 6x6:
on 12. July 2020, 19:38 by stefliew
Can't seem to fix broken image on German page
on 10. July 2020, 11:20 by ropeko
The example is missing on the German page
from stefliew: I've been trying to fix the broken image on the German page. I don't know why but the example just doesn't show up.