diff --git a/web/src/components/ClockOverlay.tsx b/web/src/components/ClockOverlay.tsx
index e6ba4ed..3abe92e 100644
--- a/web/src/components/ClockOverlay.tsx
+++ b/web/src/components/ClockOverlay.tsx
@@ -19,13 +19,16 @@ import { SKIN } from "../lib/skins";
 import { SHOW_DECORATIVE_ANIMATIONS } from "../lib/theme";
 import { Drift, type DriftField } from "./Drift";
 
+/** Beside the watch only, never behind it: on a 1080p kiosk the watch covers roughly
+ * 28-72% of the width, and a bubble rising behind it would drag the watch into every
+ * frame the Pi redraws. */
 const BUBBLES: DriftField = [
   [5, 14, 0.5, 9, 0],
   [12, 22, 0.5, 12, -3],
+  [17, 16, 0.5, 11, -2],
   [22, 10, 0.5, 8, -6],
-  [48, 16, 0.5, 11, -2],
-  [63, 12, 0.5, 10, -7],
   [78, 24, 0.5, 14, -5],
+  [83, 12, 0.5, 10, -7],
   [88, 12, 0.5, 9, -1],
   [95, 18, 0.5, 13, -9],
 ];
@@ -69,10 +72,14 @@ export function ClockOverlay({ visible, clock, onClose }: Props) {
         <div className="clock-face">
           <Dial />
           <div className="clock-hand clock-hand-hour" style={{ transform: `rotate(${angles.hour}deg)` }}>
-            <div />
+            <div>
+              <div />
+            </div>
           </div>
           <div className="clock-hand clock-hand-minute" style={{ transform: `rotate(${angles.minute}deg)` }}>
-            <div />
+            <div>
+              <div />
+            </div>
           </div>
           <div className="clock-hand clock-hand-second" style={{ transform: `rotate(${angles.second}deg)` }}>
             <div />
diff --git a/web/src/styles/clock.css b/web/src/styles/clock.css
index fac985b..0f84571 100644
--- a/web/src/styles/clock.css
+++ b/web/src/styles/clock.css
@@ -362,8 +362,12 @@
   will-change: transform;
 }
 
-.clock-hand-hour,
-.clock-hand-minute {
+/* The outline and shadow, on the hand's inner box rather than the hand: a filter on the
+   layer itself would be recomputed on the GPU every frame anything on screen moves (the
+   bubbles), while one inside it is drawn once into the layer's picture. The shape is
+   one level further in, so the outline goes round the clipped arrow, not its box. */
+.clock-hand-hour > div,
+.clock-hand-minute > div {
   filter: drop-shadow(0.35vmin 0 0 var(--clock-ink)) drop-shadow(-0.35vmin 0 0 var(--clock-ink))
     drop-shadow(0 0.35vmin 0 var(--clock-ink)) drop-shadow(0 -0.35vmin 0 var(--clock-ink))
     drop-shadow(0 1vmin 1vmin oklch(15% 0.05 210 / 0.3));
@@ -382,8 +386,18 @@
   margin-left: -2.7vmin;
 }
 
-.clock-hand-hour > div {
+.clock-hand-hour > div,
+.clock-hand-minute > div {
   bottom: -3.5vmin;
+}
+
+.clock-hand-hour > div > div,
+.clock-hand-minute > div > div {
+  position: absolute;
+  inset: 0;
+}
+
+.clock-hand-hour > div > div {
   background: oklch(92% 0.06 345);
   clip-path: polygon(50% 0%, 100% 22%, 66% 22%, 66% 100%, 34% 100%, 34% 22%, 0% 22%);
 }
@@ -394,8 +408,7 @@
   margin-left: -2.5vmin;
 }
 
-.clock-hand-minute > div {
-  bottom: -3.5vmin;
+.clock-hand-minute > div > div {
   background: oklch(92% 0.05 200);
   clip-path: polygon(50% 0%, 100% 14%, 64% 14%, 64% 100%, 36% 100%, 36% 14%, 0% 14%);
 }