diff --git a/src/wip/subproof.pysty b/src/wip/subproof.pysty
new file mode 100644
index 0000000..a474b12
--- /dev/null
+++ b/src/wip/subproof.pysty
@@ -0,0 +1,40 @@
+__HEADER__(Subproof environment with black square at end of proof.)
+
+\RequirePackage{amssymb}
+\RequirePackage{amsthm}
+\RequirePackage{xparse}
+\RequirePackage{refcount}
+\RequirePackage{translator}
+
+\usedictionary{translator-proof-dictionary}
+
+\DeclareRobustCommand{\blackqed}{%
+  \ifmmode \mathqed
+  \else
+    \leavevmode\unskip\penalty9999 \hbox{}\nobreak\hfill
+    \quad\hbox{$\blacksquare$}%
+  \fi
+}
+
+\DeclareDocumentEnvironment{subproof}{ o }
+{
+  \IfValueTF{#1}
+  {
+    \def__PACKAGE_MACRO__(subproof@prefix){#1}
+  }
+  {
+    \def__PACKAGE_MACRO__(subproof@prefix){\translate{Subproof}}
+  }
+  \pushQED
+  {
+    \blackqed
+    }%
+  \normalfont \topsep6\p@\@plus6\p@\relax
+  \trivlist
+  \item[\hskip\labelsep
+        \itshape
+    __PACKAGE_MACRO__(subproof@prefix)\@addpunct{.}]\ignorespaces
+}
+{
+  \popQED\endtrivlist\@endpefalse
+}