consolidate CSS properties for summary marker

diff --git a/src/css/doc.css b/src/css/doc.css
index 10657c0..377dd0d 100644 (file)
--- a/src/css/doc.css
+++ b/src/css/doc.css
@@ -564,8 +564,7 @@ h1.page + aside.toc.embedded {
 }
 
 .doc details[open] > summary::before {
-  border: solid transparent;
-  border-top-color: currentColor;
+  border-color: currentColor transparent transparent;
   border-width: 0.5rem 0.3rem 0;
   transform: translateY(15%);
 }