Title text:
The draw-by-repetition rule does a good job of keeping players from sliding a tile back and forth repeatedly, but the tiles definitely introduce some weird en passant and castling edge cases.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3139/
I would say you can only move a tile if you have a piece on it as well.