diff --git a/label_inscribed_600cell.js b/label_inscribed_600cell.js
index ce19883..7b5a104 100644
--- a/label_inscribed_600cell.js
+++ b/label_inscribed_600cell.js
@@ -269,3 +269,12 @@ export function equator(i600, b600, apices) {
 }
 
 
+
+
+export function antipode(shape, nid) {
+    const n0 = shape.nodes.filter((n) => n.id === nid)[0];
+    const dists = shape.nodes.map((n) => [ dist(n, n0), n ]);
+    dists.sort((a, b) => b[0] - a[0]);
+    return dists[0][1].id;
+}
+