first commit

ui/hooks/use-mobile.ts

@@ -0,0 +1,19 @@
+import * as React from "react";
+
+const MOBILE_BREAKPOINT = 768;
+
+export function useIsMobile() {
+	const [isMobile, setIsMobile] = React.useState<boolean | undefined>(undefined);
+
+	React.useEffect(() => {
+		const mql = window.matchMedia(`(max-width: ${MOBILE_BREAKPOINT - 1}px)`);
+		const onChange = () => {
+			setIsMobile(window.innerWidth < MOBILE_BREAKPOINT);
+		};
+		mql.addEventListener("change", onChange);
+		setIsMobile(window.innerWidth < MOBILE_BREAKPOINT);
+		return () => mql.removeEventListener("change", onChange);
+	}, []);
+
+	return !!isMobile;
+}