diff --git a/samples/calc-01/index.css b/samples/calc-01/index.css
index fc47346..1ad7f8f 100644
--- a/samples/calc-01/index.css
+++ b/samples/calc-01/index.css
@@ -357,6 +357,9 @@ button:active {
 .key-enter {
   background: linear-gradient(180deg, var(--key-enter-top), var(--key-enter-bottom));
   grid-row: span 2;
+  writing-mode: vertical-rl;
+  text-orientation: upright;
+  letter-spacing: 0.08em;
 }
 
 .error {