Partial rewrite, missing:

- Correctly parsing incoming messages
- Sending the gamestate after relevant actions

Mau/Player.cs

@@ -13,5 +13,25 @@ public class Player
         Connection = connection;
     }
     
-    public bool IsMe(string playerId) => Connection.ConnectionId == playerId;
+    public void GiveCard(Card card)
+    {
+        Hand.Add(card);
+    }
+    
+    public void GiveCards(IEnumerable<Card> cards)
+    {
+        Hand.AddRange(cards);
+    }
+    
+    public Card? TakeCardFromHand(Card card)
+    {
+        return Hand.FirstOrDefault(handCard => handCard.IsSameCard(card));
+    }
+    
+    public bool IsMe(string playerId) => Connection.Id == playerId;
+
+    public bool CanPlayCard(Card currentCard)
+    {
+        return Hand.Any(card => card.CanBePlayedOn(currentCard));
+    }
 }