The most useful thing you can send is a specific problem: a puzzle that seems to have no solution, a control that doesn't respond, a PDF that prints wrong, or a sentence that doesn't make sense.
Email [email protected].
If it's about a puzzle
Please include the difficulty you were playing and, if you can, the state of the grid. Puzzles are generated fresh in your browser, so we can't look yours up — a screenshot is worth more than a description.
If it's about printing
Tell us the paper size, how many puzzles per page you chose, and what your printer did with it. Packs are written as vector PDFs, so anything that prints blurry or cropped is a bug worth knowing about.