This is basically a very simple spring simulator. All springs have the same coefficient and there is some friction otherwise the system would never stop moving.
This shit was thrown together in about an hour and a half at 2AM so don't judge how sketchy it is.
Use arrow keys to move the selected object around. Press backspace to delete the current object (also, all springs attached to it). Press D to delete the selected spring. Press F to toggle the physics simulation (default on). Press H and L to cycle through springs. Press J and K to cycle through objects. Press N to add a new object. Press S to add a new spring. Press R to set the highlighted spring's real length to its current length. Press Z to fix/unfix the current object. Press G to toggle gravity (default off). Press B to toggle boundaries / bouncing (default on).