A web of point-masses connected by springs is modeled as a graph and physics calculation. Each springs ends accelerates its mass to reach the springs ideal length. The force effected in this way on a springs masses is given by a factor K specific to the spring and the distance between the current positions of the two connected masses.
The web of point-masses are edited by adding a dot and scrolling the mouse-wheel (or clicking an up/down triangle) in order to define its mass. The mass M at a given dot is indicated by the area of the drawn dot. When a dot is added and only at that time it may be connected to the existing dots. In this way the connected dots forms a graph already non-cyclic as created dot by dot, and the web can be passed as-is to the spring-model. When a dot is connected a line is drawn to it, representing a spring. The K factor of the spring is adjusted by the mouse-wheel (or alternatively by the up/down triangles). Clicking a second time on a dot will remove last added either dot or line.
When the web drawn is satisfactory to the observer, the model may be run by clicking the right-pointing triangle on the top left. Clicking anywhere once running will displace the last (the selected) point-mass added. Any other point-mass can be selected by the mouse-wheel (or clicking the arrow triangles). Clicking the upper left double-rectangle (swapped for the triangle to run) will go back to edit-mode so that additional dots and lines may be added, or the existing ones removed or the last objects respective K or M value modified.
http://maraca.name/springweb-create/
A car is controlled by mouse position, affecting with a force to its front or back. To the right is ahead, and letters will appear to collect among the platforms.