A trim simulation for sail boats that are rigged similarly to a 420 dinghy. You select a parameter, for example the Headstay-Length, and then change the value of that param with the mouse wheel. On the real boat the equivalent would be that you tighten the jib halliard watch how the mast will come forward and start to bend. Watch the graph while you scroll the mouse wheel. Text output is included and can show absolute or differential values.

I have published the computation (model) and most of the user interface (graph) as Open Source - see project RiggVar-RG38 at GitHub.