ResNet residual block

\documentclass[border=10pt]{standalone}

% --- packages (mirror these in template.meta.json "requires") ---
\usepackage{tikz}
\usetikzlibrary{arrows.meta}

% --- palette (canonical source: reference/color-palettes/color-palettes.md; light variant) ---
\definecolor{otblue}{HTML}{0072B2}
\definecolor{otorange}{HTML}{E69F00}
\definecolor{otteal}{HTML}{009E73}
\definecolor{otpurple}{HTML}{CC79A7}
\definecolor{otgray}{HTML}{5A5A5A}

\begin{document}
% ==== parameters (edit these) ============================================
% Labels of the weight-layer boxes in the residual branch, top to bottom.
% The number of entries IS the number of stacked layers (classic block = 2).
\def\branchlabels{weight layer,weight layer}
\def\actlabel{relu}                              % activation between layers and after the sum
\def\inputlabel{$\mathbf{x}$}                    % top input
\def\residuallabel{$\mathcal{F}(\mathbf{x})$}    % side label for the residual branch
\def\outputlabel{$\mathcal{F}(\mathbf{x})+\mathbf{x}$} % side label at the sum
\def\skiplabel{$\mathbf{x}$}                      % identity / skip-path label (upper)
\def\identitylabel{identity}                      % identity / skip-path label (lower)
\def\blocksep{1.8}   % vertical centre-to-centre distance between stages (cm)
\def\blockw{3.0}     % weight-layer box width (cm)
\def\blockh{0.9}     % weight-layer box height (cm)
\def\skipbow{2.7}    % how far right the identity skip connection bows out (cm)
% =========================================================================

\begin{tikzpicture}[
    >={Stealth[length=2.4mm]},
    wlayer/.style={
      draw=otblue!70!black, fill=otblue!12, rounded corners=2pt,
      line width=0.8pt, align=center, font=\sffamily\small,
      minimum width=\blockw cm, minimum height=\blockh cm,
    },
    addop/.style={
      circle, draw=otgray!85!black, line width=0.8pt,
      inner sep=1.4pt, minimum size=0.62cm, font=\small,
    },
    flow/.style={draw=otgray!85, line width=0.9pt, ->},
    skip/.style={draw=otgray!85, line width=0.9pt, ->, rounded corners=10pt},
    actlbl/.style={font=\sffamily\footnotesize, text=otgray, inner sep=2.5pt},
    sidelbl/.style={font=\small, text=otgray},
  ]

  % --- input ---
  \node[font=\bfseries] (xlabel) at (0,0) {\inputlabel};

  % --- residual branch: stack the weight-layer boxes, relu between them ---
  \foreach \lab [count=\i, remember=\i as \previ (initially 0)] in \branchlabels {
    \pgfmathsetmacro{\yy}{-\i*\blocksep}
    \node[wlayer] (wl\i) at (0,\yy) {\lab};
    \ifnum\i=1
      \draw[flow] (xlabel) -- (wl\i);
    \else
      \draw[flow] (wl\previ) -- node[actlbl, right] {\actlabel} (wl\i);
    \fi
    \global\let\nlayers\i
  }

  % --- summation node and output ---
  \pgfmathsetmacro{\sumy}{-(\nlayers+1)*\blocksep}
  \node[addop] (sum) at (0,\sumy) {$+$};
  \draw[flow] (wl\nlayers) -- (sum);
  \pgfmathsetmacro{\outy}{\sumy-0.85*\blocksep}
  \coordinate (out) at (0,\outy);
  \draw[flow] (sum) -- node[actlbl, right] {\actlabel} (out);

  % --- identity skip connection: branches off the input line, bows right,
  %     and re-enters the sum from the right ---
  \coordinate (branch)    at (0,{-0.5*\blocksep});
  \coordinate (skipright) at (\skipbow,{-0.5*\blocksep});
  \draw[skip] (branch) -- (skipright) -- (skipright |- sum) -- (sum);

  % --- side labels ---
  \pgfmathsetmacro{\leftx}{-\blockw/2-0.55}
  \pgfmathsetmacro{\midy}{-(1+\nlayers)/2*\blocksep}
  \node[sidelbl, anchor=east] at (\leftx,\midy)  {\residuallabel};
  \node[sidelbl, anchor=east] at (\leftx,\sumy)  {\outputlabel};

  \pgfmathsetmacro{\skmy}{(-0.5*\blocksep+\sumy)/2}
  \node[sidelbl, anchor=west] at (\skipbow+0.25,\skmy+0.32) {\skiplabel};
  \node[sidelbl, anchor=west] at (\skipbow+0.25,\skmy-0.10) {\identitylabel};

\end{tikzpicture}
\end{document}