diff --git a/ui/frontend/src/lib/game/game-shell.svelte b/ui/frontend/src/lib/game/game-shell.svelte
index 5e1da80..5456864 100644
--- a/ui/frontend/src/lib/game/game-shell.svelte
+++ b/ui/frontend/src/lib/game/game-shell.svelte
@@ -671,6 +671,22 @@ return to the lobby still disposes the stores via `onDestroy`.
 		overflow-y: auto;
 	}
 	@media (max-width: 767.98px) {
+		/*
+		Pin the shell to the viewport on mobile and take it out of
+		document flow. With `min-height: 100vh` the shell can overflow
+		the viewport by a few sub-pixels, which makes the document
+		scrollable; scrolling then toggles the mobile browser's dynamic
+		toolbar, resizing the viewport and the `position: fixed` overlays
+		(map-toggles menu, bottom-tab drawer, planet sheet) mid-gesture.
+		`position: fixed; inset: 0` keeps the viewport — and those
+		overlays — stable, leaving the active-view area as the single
+		internal scroll region.
+		*/
+		.game-shell {
+			position: fixed;
+			inset: 0;
+			min-height: 0;
+		}
 		.body {
 			padding-bottom: 3.25rem;
 		}