Total accumulated risk I'm a big fan of Minesweeper. Like other fans, I know that probabilities are important in this game. So, for more fun, I play on this player : < After sometime, I asked myself what's the meaning of the statistic : total accumulated risk. After checking at the code source, I know that the value of this statistic is calculated like : $$p_{n+1}=1-(1-p_n)(1-r_n)$$ Let $p_n$ is the total accumulated risk and $r_n$ the risk taken by selected this cell. (Thanks for @joriki about the corrections)

Your equation is misleading - read as an equation, it implies $P(C)=1$ or $P(T)=1$, which is most likely not the intended interpretation.

Rather, this is an update prescription, $P(T)\leftarrow1-(1-P(T)(1-P(C))$. Writing this as $p_{n+1}=1-(1-p_n)(1-r_n)$ and rearranging yields $1-p_{n+1}=(1-p_n)(1-r_n)$. Thus, this is a simple multiplicative update of the complements: The risk is the complement of the probability of survival, and the total accumulated probability of survival is the product of the individual probabilities of survival.