Dark
The dark or darkness is there to provide disguise, connected to the city of disguises, Venice. It provides a disguise to lovers, those who are trying to hide, those who are trying to disguise themselves, those like Villanelle. Darkness represents the unknown and ominous. Darkness also "fills up the space between your jacket and your heart" and it finds a way into your eyes. It is something to be afraid of, as it encompasses one's entire being; it is absolute.
Game
"You play, you win, you play, you lose. You play." The novel is "playing" with the notion that everything in life is a game. That's why we have this quote repeated several time throughout. Bonaparte's conquest is described in this way, he plays the game of conquest, feeling certain of his win, even when it seems highly unlikely, he continues to play. This game of life is literally portrayed in the scene where the rich man and a stranger gamble for life.
Maze city
Venice is described as a city of mazes. It is a city surrounded by water and watery alleys for roads. It is a place where it is easy to lose one's way and it is easy to find it. There are many directions that end at the same place. Even when one walks straight there is no road that goes straight away, and there are plenty of holes and cracks which make it possible only for rats and cats to go through. It is a city where a lot of different people seek hide-out, runaways and outcasts from different parts of the world. It is a city of disguises and an unusual city where impossible becomes possible.