Step

What Step is

Step is a free Linux desktop application for exploring physical systems through interactive simulations. It supports two-dimensional classical mechanics, molecular dynamics, sound waves, and deformable bodies. Experiments can include particles, damped springs, gravitational and Coulomb forces, rigid bodies, and collision handling. Users can change body and force properties during a running simulation. Graph, meter, and tracer tools display results, while a controller can adjust properties using custom keyboard shortcuts. Step also calculates unit conversions, expressions, error propagation, and solver error estimates. Its explicit and implicit solvers reach 8th order and can use adaptive timesteps, though most solvers require GSL. Expression calculations such as unit conversion require libqalculate. Learning materials include tutorials, sample experiments, object context details, and an integrated Wikipedia browser; more experiments are available through KNewStuff. Step is GPL-2.0+ licensed, and its StepCore simulation library can be used separately in code or other software. The listed release is Step 26.08.2, released 2026-10-08.