[feat] Support empty numeric inputs & UI improvements for real app

components/number-ball.tsx

@@ -7,7 +7,7 @@ interface NumberBallProps {
   number: number
   state: "idle" | "highlighted" | "used"
   colorIndex?: number
-  size?: "normal" | "large"
+  size?: "normal" | "large" | "xlarge"
   dimmed?: boolean
 }
 
@@ -34,6 +34,7 @@ export function NumberBall({ number, state, colorIndex, size = "normal", dimmed
         "flex items-center justify-center font-mono select-none transition-all duration-150",
         size === "normal" && "w-8 h-8 text-sm",
         size === "large" && "w-14 h-14 text-lg",
+        size === "xlarge" && "w-16 h-16 text-xl",
         dimmed && !isHighlighted && "opacity-30",
       )}
       style={{