feat: Introduce DownCount feature with new models, scripts, textures, and a dedicated quiz scene.

Assets/Quiz/Scripts/DownCount/LetterPoint.cs

@@ -0,0 +1,54 @@
+
+using UdonSharp;
+using UnityEngine;
+using VRC.SDKBase;
+using VRC.Udon;
+
+public class LetterPoint : UdonSharpBehaviour
+{
+    LetterCard heldCard;
+
+    public void OnCardReleased(LetterCard card)
+    {
+        if (heldCard != null) return;
+        heldCard = card;
+        card.transform.position = this.transform.position;
+        card.transform.rotation = this.transform.rotation;
+    }
+
+    public void OnCardRemoved(LetterCard card)
+    {
+        if (heldCard == card)
+        {
+            heldCard = null;
+        }
+    }
+
+    void OnTriggerEnter(Collider other)
+    {
+        LetterCard card = other.GetComponent<LetterCard>();
+        if (card != null)
+        {
+            card.currentPoint = this;
+        }
+    }
+
+    void OnTriggerExit(Collider other)
+    {
+        LetterCard card = other.GetComponent<LetterCard>();
+        if (card != null)
+        {
+            // If the exiting card was the one we were holding, clear it
+            if (card == heldCard)
+            {
+                heldCard = null;
+            }
+
+            // Only clear if we are the one currently registered
+            if (card.currentPoint == this)
+            {
+                card.currentPoint = null;
+            }
+        }
+    }
+}