2D Linkage Designer — interactive mechanism editor

Fixed pivot — click on the canvas to pin a joint to the ground.
Rotating joint — click to place a free pin joint.
Rigid link — click one joint, then another. Type a length and tick use value to create a link of an exact length; leave it empty to use the drawn distance. Clicking empty space creates the joint for you.
Track — click two points to lay down a rail, then use Slider and click near the rail to put a slider on it.
Motor — click a joint that has a link attached; that link becomes the driven crank. Change the driven link and the speed in the inspector.
Delete — click any joint, link, track or motor to remove it.

Play / Pause (Space) runs the motor; Step (S) advances one frame; Reset (R) returns to the design pose.
2° buttons and the crank angle slider move the driven link directly.
Drag any joint with the mouse: the solver keeps every link rigid and every slider on its rail while you pull.
Motion paths are drawn for every moving joint; Clear paths wipes them.

Rigid links keep their exact length at every step — the status bar shows the worst length error in the current pose (it should read 0.000).
Sliders stay on their rails; joints stay attached to every link that meets there.
If a motor cannot reach the commanded angle (hard stop, toggle position, jamming linkage) the simulation stops and tells you which constraint blocked it.
Tracks are ground-fixed rails. A slider riding on a moving link is not supported in this version.