Thanks for the feedback, I think I should have made that mechanism clearer!
This was my first time trying to make a game compatible with both touchscreens and a mouse. Because I needed a way to distinguish between simply clicking a tile to rotate it and actually dragging it, I went with a 'click and hold' system. If you hold it for a moment, the tile grows and flashes white to show it's ready to move. I will update the instructions on the web page