When I first played Rotohex, I understood on a basic level how I was supposed to play the game, but I couldn't imagine a distant future in which I could play the game. I could not make my mind process the act of rotating triangles to create same-colored hexagons. I think it's the hexagons -- whatever it is, it felt a lot more mentally taxing than most puzzle games, and I failed within a few minutes on my first try.
Then, during subsequent attempts, I began to experience a bit more success. I started instinctively knowing how to position blocks, without consciously knowing what was happening. The world outside of my TV dropped away and I entered a prolonged Rotohex fugue state until the rush of falling triangles overwhelmed me and, half an hour later or so, I was dumped back into reality.
To me, that combination of total focus and trancelike hypnotism is the ideal result of a good falling-block puzzle game. You sort of forget about the world, and you even forget to think about what you're doing, and things just happen on the screen as your dinner gets cold.