Solution (source code)

= Solution

The <normal line to a plane curve> is perpendicular to the <tangent line>, so its slope is the negative reciprocal $1/\sqrt6$. The required equation is
$$
\boxed{y-1=\frac1{\sqrt6}\left(x-\frac{\sqrt6}{2}\right),
\qquad\text{equivalently}\quad y=\frac{x}{\sqrt6}+\frac12.}
$$
The normal direction also agrees with the <gradient> $(4x,2y)$ of the defining level <function>.