Design your own experiments using the tools provided in the simulation to systematically identify what affects the natural resonance for mass-spring systems.  You may want to start with damping set very low.

Organize your experiments and findings in data tables and in written descriptions of what the effect of each parameter is on the oscillations of the mass-spring system.   Be sure to keep track of and record values of those parameters you are keeping constant.

Recognize that when you slowly vary the values of each parameter, you will need to watch what happens over a period of time before making more changes in value.  This is because the simulation will show transient behavior – it takes a period of time for the system to settle into some sort of constant motion, rather than instantaneously settling down.  This is a realistic representation for how things really work.

Most importantly, specifically find conditions where the mass-spring system is in steady-state resonance with the driver.