Algodoo

After several days of trying to figure out how to get a value from one geom to another through a spring, I gave up on trying to understand it and took what I was given to make something useful.
This scene contains a demo of spring fuel lines, which come in pairs. They don't have to come in pairs necessarily, but it helps understand how information moves. All springs in this scene have unequally sized endpoints. Information travels from the big end to the small end. It doesnt have to travel in one direction only, but shush.

The orange box is a fuel tank, with an internal _fuel value, which is set to its area * 600.

The dark gray polygon is a thruster, with internal values _consumption and _fuel. The _fuel value is copied from the fuel tank via the red spring. _consumption is set by code in the thruster.

The thruster has a bunch of code, such that it can only be active when there is fuel in the tank AND the thruster key ("W") is down. When active, it sets the thruster polygon's _consumption to its own value _fueluse. When not active, it sets it to 0.

The red "source" spring sets the _fuel value in the thruster polygon to the _fuel value in the tank.

The blue "drain" spring sets the tank's _fuel to itself minus the consumption value of the thruster polygon.

Off to the left is a simple diagram depicting information flow through the SWire.

This might become a new space game concept!