--- a/style.sty	Sat Sep 09 14:14:31 2023 +0100
+++ b/style.sty	Sun Sep 10 12:24:55 2023 +0100
@@ -98,3 +98,16 @@
 \def\cwFIVE{12 January}
 
 %%\def\cwISABELLE{11 December}
+
+
+%%%%%%%%%%%%%%
+%% lualatex testing commandline arguments
+\newcommand{\luaif}[1]{\ifnum1=\directlua{if #1 then tex.sprint(1) else tex.sprint(0) end} }
+
+\luaif{arg[2] == "sol"}
+\newcommand{\solution}[1]{%
+  \begin{quote}\sf%
+    #1%
+  \end{quote}} \else
+\newcommand{\solution}[1]{}
+\fi