Throw a stone and read its arc. Tilt a plane, spin a wheel, let two carts collide — every bench is a page from a working notebook: construction lines in pale ink, and every live quantity glowing as it changes.
Mechanics here is one subject with two doors. The Lab is the interactive side — fourteen modules of draggable benches with live readouts. The Full Book is the complete written textbook — every proof, worked example and problem, with the same benches surfaced inline. Enter either; every module header carries a ◈ ⇄ ▤ switch to flip between them.