Index investing is a simple, low-cost and effective investment approach where you invest in index funds that represent portions or the entirety of the market (like the S&P500). It doesn't require you to make decisions about which stocks to invest in or when to buy and sell. Market timing represents one deviation from this approach, in which the investor tries to predict when the market will go up or down and buy and sell their investments accordingly. This is a more difficult approach and in many, most(?) cases tends to underperform index investing. This game attempts to show the difficulty of market timing on real, historical data from the S&P500 (between 1/1/1950 and 2021), either sequential returns from a real period ("historical") or probabilistic returns based on the distribution of returns over the 68 year dataset ("Monte Carlo").