% Case 2 (x < 0): derp.
%
-% Used below to define pcases.
-\usepackage{enumitem}
+% Used below to define pcases. The ``loadonly'' parameter prevents
+% a very bad interaction with the beamer document class.
+\usepackage[loadonly]{enumitem}
% Needed to perform division in the definition of \singleblskip.
\usepackage{calc}