Machinations.io is a fairly rare breed, a tool dedicated to game design. Currently in a free beta, Machinations is a browser based tool for designing and simulating mechanics for gameplay.
Descriptions for the Machinations.io website FAQ:
Machinations.io is a browser-based platform to design, balance and simulate game systems. It allows you to map any game system in an interactive diagram, set parameters that define elements and the relationship between them, and visualise the way in which these systems work. Based on that, you can simulate different outcomes, plot results and balance your game economy.
If you are familiar with diagramming software like Visio or have used a mind mapping application, you have a decent understanding of Machinations. Machinations is however one of those tools that is easier to understand when seen in action, so I would recommend watching the video below.
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