Lecture 2: Linkages, configurations, configuration space, trace; Kempe Universality Theorem, his proof, the bug; topological universality; signing your name
Page 2: Kempe's Universality Theorem, rhombus construction, reduction to trigonometry
You can view Kempe's related book, How To Draw A Straight Line.
These are rough, personal lecture notes handwritten by Erik Demaine used during lecture. Their primary purpose is for reading/review by students of the class.