The model simulates various lifepaths and figures the chances of retirees having enough money for the rest of their lives.

FORBES: We Are Not Prepared for Long-Term Care

But a new model that simulates the birth and evolution of planets shows that conditions need to be just, just right to get a solar system like ours.

NPR: What Makes Our Solar System Special?

Ms. McAlister recommends that beginners opt for a full-size 88-key model that has a "weighted action, " which simulates the feel of actual piano hammers.

WSJ: Digital Pianos: Great Performers for Tight Spaces