diff --git a/custom.css b/custom.css
index f2f4dcd..6416b63 100644
--- a/custom.css
+++ b/custom.css
@@ -179,6 +179,17 @@ h1, h2, h3 {
   backdrop-filter: none;
 }
 
+/* Portal narrows a card's padding on a small screen; the rule above is
+   unconditional and this sheet loads after portal's, so without this the
+   desktop padding survived onto a phone - 1.8rem of margin either side of
+   a 360px screen, a tenth of the width given to nothing. Same breakpoint
+   portal uses, so the two stay in step. */
+@media (width <= 40rem) {
+  .alt-card {
+    padding: 1.4rem 1.35rem 1.45rem;
+  }
+}
+
 .alt-card h2 {
   font-size: 1.45rem;
   margin: 0 0 0.35rem;