\(\begin{align} b &= \text{bottom}\\ t &= \text{top} \end{align}\)
\(\text{normal}(b,t) = t\)
\(\text{add}(b,t) = \text{clamp}(b+t)\)
\(\text{sub}(b,t) = \text{clamp}(b-t)\)
\(\text{diff}(b,t) = \max(b-t,t-b)\)
\(\text{mul}(b,t) = bt\)