Build an interactive 2D mechanical linkage designer.
Users should be able to:
- create fixed pivots
- create rotating joints
- create rigid links with exact lengths
- create sliders constrained to tracks
- connect components into mechanisms
- choose a driving joint or motor
- play, pause, reset, and step the simulation
- display joint coordinates and link lengths
- save and reload mechanisms
Support at least:
- a four-bar linkage
- a crank-slider mechanism
Rigid links must preserve their lengths throughout the simulation, and constrained joints must remain attached.
