I'd say drop the "predictions" angle, and focus on this: "We wanted a simple system to keep an balance, as well as take buy/sell trades as realistic as possibl

I'd say drop the "predictions" angle, and focus on this: "We wanted a simple system to keep an balance, as well as take buy/sell trades as realistic as possible." I'd love a system that would let me test ideas on historical ticker data (last 5 years would be a good start). In my mind, it works like this: You start with a fixed amount of virtual money, and you set the date to some specific day in the past. Then, you can buy and sell at whatever the market price was at that particular point in time. Once you're happy with your portfolio, you can advance the clock a few minutes, hours, or weeks, and see how you would have done. Essentially, I want the ability to quickly test trading strategies that would normally occur over a much longer period of time. Add in some screening tools, etc, and you have something I've been wishing for for many years.