Classical linear controls is a subject that is unfortunately glossed over by worn out engineers during their upper level undergraduate course work. Many do not see the subject at all, or they gain only a vague understanding while breezing through some abstract, graphical, Matlab Simulink excercises. This is a bit of a shame because linear feedback control is a wonderful subject rich both in theory and application. Bobble-Bot was invented to provide students and educators with a platform for experimenting with feedback control in a fun and engaging way. This series of blog posts will show how to use Bobble-Bot to have fun exploring this fascinating subject with entirely free and open source software. Part one will focus on keeping Bobble-Bot upright by using a PD controller. Don't know what that is? Read on to find out.