S.I.M.P.L.E. is a lightweight, browser-based language for building, simulating, and sharing system dynamics models. A direct descendant of the DYNAMO simulation language used from the late 1950s through the 1980s, reimagined for the modern web. No install required.
A complete system dynamics environment in your browser.
Write models in plain English-like syntax. Define stocks, flows, auxiliaries, and constants with minimal boilerplate.
Hit Run and see results immediately. Euler integration built in with configurable time steps.
Auto-generated time series plots and interactive causal loop diagrams. Export as SVG, PNG, or PDF.
Sign in with Google or email and save your models to the cloud. Access them from any device, anywhere.
Browse and learn from models shared by the community. Upload your own to help others learn system dynamics.
Runs entirely in the browser. Works on desktop, tablet, and mobile. Nothing to download or configure.
The S.I.M.P.L.E. language reads like a description of your system. Define stocks, flows, and relationships in a clear, readable format that anyone can understand.
The name itself is a nod to history. In 1958, MIT programmer Richard Bennett created a system called SIMPLE — "Simulation of Industrial Management Problems with Lots of Equations" — as a proof-of-concept for Jay Wright Forrester's industrial dynamics work. That prototype evolved into DYNAMO (DYNAmic MOdels), a dedicated simulation language developed by Dr. Phyllis Fox, Alexander L. Pugh III, Grace Duren, and others at the MIT Computation Center.
DYNAMO became the standard tool for system dynamics modeling for nearly three decades. It powered the groundbreaking resource depletion simulations behind the Club of Rome's Limits to Growth report and was applied across fields from urban planning to population studies. The language prioritized accessibility over programming expertise — letting researchers and analysts describe systems rather than write software. It progressed from mainframes to minicomputers in the late 1970s and arrived on personal computers as "micro-Dynamo" in the early 1980s, going through several revisions up to DYNAMO IV in 1983.
S.I.M.P.L.E. SD carries that same philosophy into the browser age: anyone should be able to model a dynamic system without being a programmer first.
Try It Now →Jump into the editor and start building your first system dynamics model in minutes.
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