diff --git a/docs/interface/flow-editor.md b/docs/interface/flow-editor.md
index 5ab659e..eb9168b 100644
--- a/docs/interface/flow-editor.md
+++ b/docs/interface/flow-editor.md
@@ -10,7 +10,9 @@ The graph runs left to right on desktop and top to bottom on phones.
 - **Nodes** show their execution status.
 - **Edges** pulse when values pass through. Click one to inspect its payload.
 - **Endpoints** show flow inputs, dashboard widgets and nodes in other flows
-  that exchange messages with this flow.
+  that exchange messages with this flow. A value passing lights one up in a
+  sweep: left to right when it sends into the flow, right to left when it reads
+  out of it.
 
 Values update over a websocket. A connection banner tells you when the editor
 cannot reach the engine.