Miura-ori launching a ball. (a) The construction disposed vertically with a ball on it. x is the vertical coordinate of the ball measured from the initial position of its center of mass, the origami being in the folded state. (b) A single crease within the entire construction. Each of the angles ϕ_i corresponds to one of the types of folds. For the case of a standard flat Miura-ori presented in this figure, there are two different types of folds: near the side a and near the side b.