diff --git a/doc/fmt.css b/doc/fmt.css
new file mode 100644
index 00000000..41cc8a20
--- /dev/null
+++ b/doc/fmt.css
@@ -0,0 +1,9 @@
+code.grammar {
+  display: block;
+  padding: 1em;
+  font-size: .8em;
+}
+
+code.grammar::first-line {
+  line-height: 0;
+}