the class time, for me, is terrible. it rarely starts on time, lacks structure, and leaves very little to take away.

physics engines:

does not calculate on the basis of time; but calculates in-betweens

matter classes:

Engine (world)
Bodies (create objects)
Body (methods to apply)
Composite (relationships between objects & world)
Render (draws to canvas)
Constrains (attachments)

doing:

const {Engine, Bodies, Composite, Body, Vector, Render} = Matter;

allows you to call stuff like Engine.create() which is the same as Matter.Engine.create().