diff --git a/NucleicRemote/NucleicRemote/Views/Theme.swift b/NucleicRemote/NucleicRemote/Views/Theme.swift
index 0efe699..d0af6c2 100644
--- a/NucleicRemote/NucleicRemote/Views/Theme.swift
+++ b/NucleicRemote/NucleicRemote/Views/Theme.swift
@@ -44,6 +44,13 @@ enum Palette {
         default: success
         }
     }
+
+    /// Activity-grid shade for a continuous brightness in `0…1` (relative to the user's own
+    /// activity, outliers excluded — see `ActivityScale`). `0` is an empty day's neutral gray.
+    /// Mirrors the Mac's `AppPalette.activity(intensity:)`.
+    static func activity(intensity: Double) -> Color {
+        intensity <= 0 ? Color.secondary.opacity(0.15) : success.opacity(intensity)
+    }
 }
 
 /// Status glyph + label, matching the Mac semantics (UX_MACOS §1).