app: Mobile grid improvements

src/hooks/useGridSpans.ts

@@ -1,13 +1,18 @@
 import { useWindowSize } from "react-use";
 
+const MOBILE_BREAKPOINT = 536;
+
 const GRID_PADDING = 32; // .grid-container { padding }
 const TOOLBAR_WIDTH = 17; // IS THIS BROWSER-SPECIFIC?
 const MAX_GRID_WIDTH = 1120; // .grid { max-width }
 const ITEM_WIDTH = 168; // .grid-item { width; height; margin }
+const ITEM_WIDTH_MOBILE = 108; // .grid-item { width; height; margin }
 
 export default (): number => {
   const { width } = useWindowSize();
+  const itemWidth = width <= MOBILE_BREAKPOINT ? ITEM_WIDTH_MOBILE : ITEM_WIDTH;
+
   return Math.floor(
-    Math.min(width - GRID_PADDING - TOOLBAR_WIDTH, MAX_GRID_WIDTH) / ITEM_WIDTH
+    Math.min(width - GRID_PADDING - TOOLBAR_WIDTH, MAX_GRID_WIDTH) / itemWidth
   );
 };