header-boxes.tex

\usepackage[most]{tcolorbox}
\usepackage{xparse}

%\definecolor{teal}{HTML}{ba5536}
%\definecolor{terra}{HTML}{363237}
\definecolor{teal}{HTML}{34675c}
\definecolor{terra}{HTML}{324851}

% plain box:
\newtcolorbox{justabox}{
  enhanced,
  colback=terra!2!white,
  colframe=terra!80!white,
  boxrule=0.3mm,
  drop small lifted shadow,
  beforeafter skip=\baselineskip,
}

% Definition environment with counter:
\newtcbtheorem[number within=chapter]{definition}{Definition}{%
  enhanced,
  breakable,
  enhanced jigsaw,
  colback=terra!2!white,
  colframe=terra!80!white,
  colbacktitle=terra!2!white,
  boxrule=0.3mm,
  drop small lifted shadow,
  titlerule=-0.5mm,
  toptitle=2mm,
  beforeafter skip=\baselineskip,
  fonttitle=\upshape\bfseries\sffamily,
  coltitle=terra!90!black,
  fontupper=\normalfont,
  }{def}

% Observation environment without title bar:
\newtcbtheorem[number within=chapter]{obs}{Observation}{%
  theorem style=plain,
  enhanced,
  colback=terra!2!white,
  colframe=terra!80!white,
  boxrule=0.3mm,
  beforeafter skip=\baselineskip,
  fonttitle=\upshape\bfseries\sffamily,
  coltitle=terra!90!black,
  fontupper=\normalfont,
  drop small lifted shadow,
  }{obs}
\newenvironment{observation}[1]{\begin{obs}{}{#1}}{\end{obs}}

% Theorem environment without 'Theorem' label:
\newenvironment{theorem}[2]{%
  \begin{tcolorbox}[%
    enhanced,
    title={#1},
    colframe=terra!80,
    colback=terra!2!white,
    colframe=terra!80!white,
    colbacktitle=terra!2!white,
    coltitle=terra!90!black,
    boxrule=0.3mm,
    titlerule=-0.5mm,
    toptitle=2mm,
    fonttitle=\upshape\bfseries\sffamily,
    drop small lifted shadow,
    beforeafter skip=\baselineskip,
    ]\label{thm:#2}%
  }%
  {\end{tcolorbox}}

% Proof:
\renewtcolorbox{proof}{
  blanker,enforce breakable,left=3mm,
  before skip=10pt,after skip=10pt,
  parbox=false, % for paragraph indentation
  borderline west={0.2mm}{0pt}{terra!60!white}
}

% semantics:

\usepackage{wrapfig}
\let\description=\eqlist
\let\enddescription=\endeqlist
\let\eqlistlabel\descriptionlabel
\newenvironment{semantics}{\begin{description}}{\end{description}}


% exercises and solutions:

\ifcompilesolutions

\usepackage[clear-aux]{xsim}
\xsimsetup{
  exercise/template=tcb,
  exercise/within=chapter,
  exercise/the-counter = \thechapter.\arabic{exercise},
  solution/template=tcbsol,
  solution/name=Exercise,
  print-solutions/headings=false,
  split-aux-lists=|--INTERNAL--||
}

\DeclareExerciseEnvironmentTemplate{tcb} {%
  \tcolorbox[
  breakable,
  enhanced jigsaw,
  fonttitle=\sffamily\upshape\bfseries,
  coltitle=teal!10!white,
  colback=teal!02!white,
  colbacktitle=teal,
  colframe=teal!70!black,
  boxrule=0.3mm,
  attach boxed title to top left={yshift=-1mm, xshift=1mm},
  beforeafter skip=.9\baselineskip,
  title = Exercise~\GetExerciseProperty{counter}%
        \GetExercisePropertyT{subtitle}{ \textit{\PropertyValue}}%
        \IfInsideSolutionF{%
            \GetExercisePropertyT{points}{ % notice the space
                (%
                \PropertyValue
                \IfExerciseGoalSingularTF{points}
                    {\XSIMtranslate{point}}
                    {\XSIMtranslate{points}}%
                )%
            }%
        }%
    ]%
    % \IfInsideSolutionT{%
    %   \tcbsubtitle{Exercise}
    %   \input{\jobname-\ExerciseType-\ExerciseID-exercise-body.tex}
    %   \tcbsubtitle{Solution}
    % }
}{\endtcolorbox}

% Solution headings:
\DeclareExerciseEnvironmentTemplate{tcbsol}{%
  \tcbox[
  fontupper=\sffamily\upshape\bfseries,
  coltext=teal!10!white,
  colback=teal!80!white,
  colframe=teal!50!white,
  boxrule=0.3mm,
  boxsep=-0.5mm,
  before skip=\baselineskip,
  after skip=0.5\baselineskip,
  ]{Exercise~\GetExerciseProperty{counter}}
  \noindent
}

\else

\newtcolorbox[auto counter,number within=chapter]{exercise}{
  breakable,
  enhanced jigsaw,
  fonttitle=\sffamily\upshape\bfseries,
  coltitle=teal!10!white,
  colback=teal!02!white,
  colbacktitle=teal,
  colframe=teal!70!black,
  boxrule=0.3mm,
  attach boxed title to top left={yshift=-1mm, xshift=1mm},
  beforeafter skip=.9\baselineskip,
  title=Exercise~\thetcbcounter,
}
\usepackage{comment}
\excludecomment{solution}
\newcommand{\printsolutions}{}

\fi

% \DeclareExerciseType{exercise}{
%     exercise-env=ltxexercise,
%     solution-env=ltxsolution,
%     exercise-name=\XSIMtranslate{exercise},
%     solution-name=\XSIMtranslate{solution},
%     exercise-template=tcb,
%     solution-template=tcb,
%     within=chapter,
% }

% ========== custom list format in exercises ===========

\usepackage[shortlabels]{enumitem} % begin{enumerate}[(a)] and itemsep
\newenvironment{exlist}{\vspace{-2mm}\begin{enumerate}[(a)]\itemsep-1.5mm}{\end{enumerate}\vspace{-5mm}}
\newenvironment{sollist}{\vspace{-5mm}\begin{enumerate}[(a)]\itemsep-1.5mm}{\end{enumerate}\vspace{-3mm}}
\newcommand{\beginwithlist}{\vspace{1mm}}
\setlist[itemize]{leftmargin=*}
\setlist[enumerate]{leftmargin=*}