I know this doesn't really matter for the simulation, but you can't really have a bell curve with just two values ... -1 and 1 ... correct? It would be a uniform distribution. Or am I missing something.
To simulate a 60% win rate, the script uses a Gaussian distribution. A more common solution is generating random numbers uniformly distributed over [0,1], and then applying the "is random number < 0.6" test.
So it's not the result (-1 or 1) that is normally distributed, but rather the random numbers used in the simulation.
Mr Subliminal is correct about the Gaussian distribution.
I put that in to try to reflect my observation that trading often results in winning or losing streaks. I don't know if the idea of a Gaussian distribution doing this is mathematically correct though. And even though math was one of my best subjects in school, it's been a long time since I've been in school.

