A method, computer system and computer program product for providing a computer simulation that provides advance notification of expected events or states, comprising running a first computer simulation; running a second computer simulation corresponding to said first simulation, said second simulation having progressed further than said first simulation; and using said second computer simulation to provide information representing expected future events in said first simulation. A first computer simulation may be based on a model of a simulated system, said model having a plurality of state variables. Input data from a first user input interface may represent user interaction with said first computer simulation, while input data from a second user input interface may represent the extent to which a condition should be present in said simulation. Input from the said second user input interface is translated to values for one or more state variables in said first computer simulation consistent with a description of said condition in terms of rules embodied in the model. The representation of expected future events allows interactive fine tuning of the condition in the model.