If I'm not playing something fun in a few minutes, I'm probably going to bounce off. I'm not here to watch a movie.
I don't want to watch a long intro. I don't want a lot of cut scenes and exposition up front.
The dark souls games have a little cut scene that you can skip, and then you're off to playing. Perfect.
Half your age plus 7 is an okay rule for finding the floor. Don't aim for the floor. Plus 10 is less eyebrow raising.