They're not like clock-hands where they each spin freely, they block each other, you have to move them out of the way. (You don't need to cross them, they'll always be in the same order.)
You can play by yourself because it's possible to run two copies of the game. But be aware that they'll share a save-game so one will wipe out the other's. It might be possible to get them to use different folders for save-games, but I haven't gotten it working correctly yet. I'll post if I do.
It's in the "Top New Games".
:S
But I solved the problem.
I downloaded the game on my cell phone (App by APKAward) and played it simultaneously on my PC and cell phone.
It was even more fun than with two people.