Super Stitions

One of the things I like about the idea of Karma is the notion that there is some sort of payback. Life and luck aren't generated spontaneously. In some ways, this metaphysical theory is subject to physical laws: you get back what you put in. That was the jumping off point for the train of thought that I followed on my bike ride to work late last week.
I saw a black cat start to cross the street in front of me, and whether it was simply a moment of feline indecision or the sound of my approaching bike tires, he turned and slunk back into the shadows beneath a parked car. Whatever bad luck that might have come my way was circumvented by the mechanism of my bicycle or the food that cat had eaten the night before that kept him from making his mad dash across my path. A block further down the street, another cat was more assertive. This one made it across the street in front of me without much hesitation. I noticed that this one was mostly black, with white paws and chin. That's when I began to speculate on the bad luck ratio that is described by the relative blackness of the cat which crosses one's path. If the cat is fully black, but turns back is there any bad luck delivered, or will it simply dissipate without having made the full connection? Would it take a white cat going the opposite direction to counteract any of the bad ju-ju created by its darker cousin? How about if any one of them happened to walk under a ladder on the way, or broke a mirror? If I had stopped to pick up a penny a block before, would it be a wash?
Then a crow flew out of a tree and flew on ahead of me for a while. If birds are somehow opposed to cats, would this black bird have an impact on my fate, or would its blackness be the operative detail? It occurred to me briefly that another choice I had was simply to turn around and go home, avoiding the entire scenario. Or maybe it's all a lot of hooey. I just crossed my fingers and turned around three times after that last one. Just in case.