Simulink is described as '® is a block diagram environment for multidomain simulation and Model-Based Design. It supports simulation, automatic code generation, and continuous test and verification of embedded systems' and is an app. There are more than 25 alternatives to Simulink for a variety of platforms, including Windows, Linux, Mac, Web-based and SaaS apps. The best Simulink alternative is Circuit JS, which is both free and Open Source. Other great apps like Simulink are Xcos, SimulIDE, Ktechlab and OpenModelica.
This only simulates circuits, and while it definitely works for circuits the UI is awkward.