We have not been able to do some of the simulation labs, especially those that require very small battery internal resistance. I see that you have recently updated the resistance scale on the " Circuit- Construction - Kit - DC - Virtual -Lab" to include one-tenth of a resistor, but not on the battery internal resistance scale. I hope you would take this into consideration when you do your next update. Also you should include a meter bridge in the tool set to enable student perform potentiometer experiment.