machinations.ie The Game Design Tool (for modelling and simulation and...)

machinations.ie The Game Design Tool (emphasis on The) https://machinations.io/

This is an amazing evolving web tool for flowcharting game design, for modelling resources, resource flows, and simulating game behavioural performance. 

A screenshot from machinations.io https://machinations.io/

Think of it as an Economy for your game! For modelling playability, difficulty, resource parameters. From enemy spawn rates to in-game monetisation.