diff --git a/src/Aiursoft.ChessServer/Attributes/ValidNickName.cs b/src/Aiursoft.ChessServer/Attributes/ValidNickName.cs
new file mode 100644
index 0000000..8f5c182
--- /dev/null
+++ b/src/Aiursoft.ChessServer/Attributes/ValidNickName.cs
@@ -0,0 +1,20 @@
+using System.ComponentModel.DataAnnotations;
+using System.Text.RegularExpressions;
+
+namespace Aiursoft.ChessServer.Attributes;
+
+public class ValidNickName : ValidationAttribute
+{
+    private readonly string _keyWordRegex = "^[-a-zA-Z0-9_]+$";
+
+    public override bool IsValid(object? value)
+    {
+        var regex = new Regex(_keyWordRegex, RegexOptions.Compiled);
+        return value is string input && regex.IsMatch(input);
+    }
+
+    protected override ValidationResult? IsValid(object? value, ValidationContext validationContext)
+    {
+        return this.IsValid(value) ? ValidationResult.Success : new ValidationResult("The " + validationContext.DisplayName + " can only contain numbers, alphabet and underline.");
+    }
+}
\ No newline at end of file
diff --git a/src/Aiursoft.ChessServer/Controllers/HomeController.cs b/src/Aiursoft.ChessServer/Controllers/HomeController.cs
index 6d4a812..a8eaa6f 100644
--- a/src/Aiursoft.ChessServer/Controllers/HomeController.cs
+++ b/src/Aiursoft.ChessServer/Controllers/HomeController.cs
@@ -18,18 +18,41 @@ public class HomeController : Controller
         _database = database;
     }
 
+    [HttpGet]
     public IActionResult Index()
     {
         var model = new IndexViewModel(_database.Challenges);
         return View(model);
     }
+
+    [HttpGet]
+    public IActionResult Auto(Guid playerId)
+    {
+        // I created a challenge. Go to my challenge.
+        var iHaveAChallenge = _database.Challenges.FirstOrDefault(t => t.Value.Creator.Id == playerId);
+        if (iHaveAChallenge.Value != null)
+        {
+            return RedirectToAction(nameof(Challenge), new { id = iHaveAChallenge.Key, playerId });
+        }
+        
+        // Exists a public challenge. Go to that challenge.
+        var otherChallenge = _database.Challenges.FirstOrDefault(t => t.Value.Permission == ChallengePermission.Public);
+        if (otherChallenge.Value != null)
+        {
+            return RedirectToAction(nameof(Challenge), new { id = otherChallenge.Key, playerId });
+        }
+        
+        // Create a new challenge.
+        return RedirectToAction(nameof(Create), new { playerId });
+    }
     
+    [HttpGet]
     public IActionResult Create(Guid playerId)
     {
         var iHaveAChallenge = _database.Challenges.FirstOrDefault(t => t.Value.Creator.Id == playerId);
         if (iHaveAChallenge.Value != null)
         {
-            return RedirectToAction(nameof(Room), new { id = iHaveAChallenge.Key });
+            return RedirectToAction(nameof(Challenge), new { id = iHaveAChallenge.Key, playerId });
         }
         var model = new CreateChallengeViewModel();
         return View(model);
@@ -38,6 +61,11 @@ public class HomeController : Controller
     [HttpPost]
     public IActionResult Create(CreateChallengeViewModel model)
     {
+        if (!ModelState.IsValid)
+        {
+            return View(model);
+        }
+        
         var player = _database.GetOrAddPlayer(model.CreatorId);
         var challenge = new Challenge(player)
         {
@@ -46,14 +74,38 @@ public class HomeController : Controller
             Permission = model.Permission,
             TimeLimit = model.TimeLimit,
         };
-        var uniqueId = _counter.GetUniqueNo();
-        _database.Challenges.TryAdd(uniqueId, challenge);
-        return RedirectToAction(nameof(Room), new { id = uniqueId });
+        var roomId = _counter.GetUniqueNo();
+        _database.Challenges.TryAdd(roomId, challenge);
+        return RedirectToAction(nameof(Challenge), new { id = roomId, playerId = model.CreatorId });
     }
 
-    public IActionResult Room(int id)
+    [HttpGet]
+    public IActionResult Challenge(int id, Guid playerId)
     {
-        // Not implemented.
-        return Ok();
+        var player = _database.GetOrAddPlayer(playerId);
+        var challenge = _database.GetOrAddChallenge(id, player);
+        var model = new ChallengeViewModel()
+        {
+            RoomId = id,
+            PlayerId = playerId,
+            IsCreator = challenge.Creator.Id == playerId,
+        };
+        return View(model);
+    }
+    
+    [HttpPost]
+    public IActionResult DropChallenge(DropChallengeViewModel model)
+    {
+        if (!ModelState.IsValid)
+        {
+            return RedirectToAction(nameof(Challenge), new { id = model.Id, playerId = model.PlayerId });
+        }
+        var player = _database.GetOrAddPlayer(model.PlayerId);
+        var challenge = _database.GetOrAddChallenge(model.Id, player);
+        if (challenge.Creator.Id == model.PlayerId)
+        {
+            _database.Challenges.TryRemove(model.Id, out _);
+        }
+        return RedirectToAction(nameof(Index));
     }
 }
\ No newline at end of file
diff --git a/src/Aiursoft.ChessServer/Controllers/PlayersController.cs b/src/Aiursoft.ChessServer/Controllers/PlayersController.cs
index 86816d6..0e97b00 100644
--- a/src/Aiursoft.ChessServer/Controllers/PlayersController.cs
+++ b/src/Aiursoft.ChessServer/Controllers/PlayersController.cs
@@ -1,6 +1,6 @@
 using System.ComponentModel.DataAnnotations;
+using Aiursoft.ChessServer.Attributes;
 using Aiursoft.ChessServer.Data;
-using Aiursoft.CSTools.Attributes;
 using Microsoft.AspNetCore.Mvc;
 
 namespace Aiursoft.ChessServer.Controllers;
@@ -24,7 +24,7 @@ public class PlayersController : ControllerBase
     
     [HttpPut]
     [Route("{id:guid}/new-name/{nickname}")]
-    public IActionResult ChangeNickname([Required]Guid id, [Required][MaxLength(20)][ValidDomainName]string nickname)
+    public IActionResult ChangeNickname([Required]Guid id, [Required][MaxLength(20)][ValidNickName]string nickname)
     {
         if (ModelState.IsValid == false)
         {
diff --git a/src/Aiursoft.ChessServer/Data/InMemoryDatabase.cs b/src/Aiursoft.ChessServer/Data/InMemoryDatabase.cs
index 44a4ec4..6b6df3f 100644
--- a/src/Aiursoft.ChessServer/Data/InMemoryDatabase.cs
+++ b/src/Aiursoft.ChessServer/Data/InMemoryDatabase.cs
@@ -35,4 +35,12 @@ public class InMemoryDatabase : ISingletonDependency
             });
         }
     }
+    
+    public Challenge GetOrAddChallenge(int id, Player creator)
+    {
+        lock (Challenges)
+        {
+            return Challenges.GetOrAdd(id, _ => new Challenge(creator));
+        }
+    }
 }
\ No newline at end of file
diff --git a/src/Aiursoft.ChessServer/Models/ViewModels/ChallengeViewModel.cs b/src/Aiursoft.ChessServer/Models/ViewModels/ChallengeViewModel.cs
new file mode 100644
index 0000000..891c89b
--- /dev/null
+++ b/src/Aiursoft.ChessServer/Models/ViewModels/ChallengeViewModel.cs
@@ -0,0 +1,10 @@
+namespace Aiursoft.ChessServer.Models;
+
+public class ChallengeViewModel
+{
+    public int RoomId { get; set; }
+    
+    public Guid PlayerId { get; set; }
+    
+    public bool IsCreator { get; set; }
+}
\ No newline at end of file
diff --git a/src/Aiursoft.ChessServer/Models/ViewModels/CreateChallengeViewModel.cs b/src/Aiursoft.ChessServer/Models/ViewModels/CreateChallengeViewModel.cs
index ba9af36..ac07771 100644
--- a/src/Aiursoft.ChessServer/Models/ViewModels/CreateChallengeViewModel.cs
+++ b/src/Aiursoft.ChessServer/Models/ViewModels/CreateChallengeViewModel.cs
@@ -1,14 +1,23 @@
-namespace Aiursoft.ChessServer.Models;
+using System.ComponentModel.DataAnnotations;
+
+namespace Aiursoft.ChessServer.Models;
 
 public class CreateChallengeViewModel
 {
-    public Guid CreatorId { get; set; }
+    [Required]
+    public Guid CreatorId { get; init; }
     
-    public string Message { get; set; } = "A chess room.";
+    [Required]
+    [MinLength(3)]
+    [MaxLength(20)]
+    public string Message { get; init; } = "A chess room.";
     
-    public RoleRule RoleRule { get; set; } = RoleRule.Random;
+    [Required]
+    public RoleRule RoleRule { get; init; } = RoleRule.Random;
     
-    public TimeSpan TimeLimit { get; set; } = TimeSpan.FromMinutes(10);
+    [Required]
+    public TimeSpan TimeLimit { get; init; } = TimeSpan.FromMinutes(10);
     
-    public ChallengePermission Permission { get; set; } = ChallengePermission.Public;
+    [Required]
+    public ChallengePermission Permission { get; init; } = ChallengePermission.Public;
 }
\ No newline at end of file
diff --git a/src/Aiursoft.ChessServer/Models/ViewModels/LeaveRoomViewModel.cs b/src/Aiursoft.ChessServer/Models/ViewModels/LeaveRoomViewModel.cs
new file mode 100644
index 0000000..d1bad1f
--- /dev/null
+++ b/src/Aiursoft.ChessServer/Models/ViewModels/LeaveRoomViewModel.cs
@@ -0,0 +1,15 @@
+using System.ComponentModel.DataAnnotations;
+using Microsoft.AspNetCore.Mvc;
+
+namespace Aiursoft.ChessServer.Models;
+
+public class DropChallengeViewModel
+{
+    [FromRoute]
+    [Required]
+    public int Id { get; set; }
+    
+    [FromForm]
+    [Required]
+    public Guid PlayerId { get; set; }
+}
\ No newline at end of file
diff --git a/src/Aiursoft.ChessServer/Views/Home/Challenge.cshtml b/src/Aiursoft.ChessServer/Views/Home/Challenge.cshtml
new file mode 100644
index 0000000..551e8d3
--- /dev/null
+++ b/src/Aiursoft.ChessServer/Views/Home/Challenge.cshtml
@@ -0,0 +1,38 @@
+@model Aiursoft.ChessServer.Models.ChallengeViewModel
+
+<div class="jumbotron">
+    <div class="container">
+        <h1 class="display-4">Waiting for joining...</h1>
+        <p class="lead">Please share the link of this room to your friend!</p>
+        @{
+            var link = $"{Context.Request.Scheme}://{Context.Request.Host}/Home/Room/{Model.RoomId}";
+        }
+        <form asp-controller="Home" asp-action="DropChallenge" asp-route-id="@Model.RoomId" method="post" class="d-inline" asp-antiforgery="false">
+            <div asp-validation-summary="All" class="text-danger"></div>
+            <input type="hidden" name="playerId" value="@Model.PlayerId"/>
+            
+            <input type="text" class="form-control" value="@link" readonly>
+            <a class="btn btn-secondary btn-lg mt-4" data-clipboard-text="@link" role="button" data-toggle="tooltip" data-placement="top" title="Copied!">
+                Copy link
+            </a>
+            <button type="submit" class="btn btn-danger btn-lg mt-4">
+                Leave
+            </button>
+        </form>
+    </div>
+</div>
+
+@section scripts
+{
+    <script src="/node_modules/clipboard/dist/clipboard.min.js"></script>
+    <script>
+        // Initialize clipboard.
+        const clipboard = new ClipboardJS('.btn');
+        
+        // Activate tooltip tool
+        $('[data-toggle="tooltip"]').tooltip({
+                trigger: 'click',
+                placement: 'bottom'
+        });
+    </script>
+}
\ No newline at end of file
diff --git a/src/Aiursoft.ChessServer/Views/Home/Create.cshtml b/src/Aiursoft.ChessServer/Views/Home/Create.cshtml
index 73ca529..bc40746 100644
--- a/src/Aiursoft.ChessServer/Views/Home/Create.cshtml
+++ b/src/Aiursoft.ChessServer/Views/Home/Create.cshtml
@@ -15,7 +15,8 @@
         <div class="card mb-2 col-sm-12 px-1">
             <div class="card-body">
                 <h5 class="card-title">Create a new room</h5>
-                <form asp-controller="Home" asp-action="Create" method="post">
+                <form asp-controller="Home" asp-action="Create" method="post" asp-antiforgery="false">
+                    <div asp-validation-summary="All" class="text-danger"></div>
                     <input type="hidden" asp-for="CreatorId"/>
                     <div class="form-group">
                         <label asp-for="Message"></label>
diff --git a/src/Aiursoft.ChessServer/Views/Home/Index.cshtml b/src/Aiursoft.ChessServer/Views/Home/Index.cshtml
index 8be97e4..871f903 100644
--- a/src/Aiursoft.ChessServer/Views/Home/Index.cshtml
+++ b/src/Aiursoft.ChessServer/Views/Home/Index.cshtml
@@ -5,7 +5,7 @@
         <h1 class="display-4">Welcome challenger!</h1>
         <p class="lead">Join a room, or create a room!</p>
         <p>
-            <button class="btn btn-success btn-lg mt-4" role="button">Auto join</button>
+            <a class="btn btn-success btn-lg mt-4" role="button" id="autoButton" asp-controller="Home" asp-action="Auto" >Auto join</a>
             <a class="btn btn-secondary btn-lg mt-4" role="button" id="createButton" asp-controller="Home" asp-action="Create">Create a new room</a>
         </p>
     </div>
@@ -47,11 +47,13 @@
     <script type="module">
         import { getUserId } from "/scripts/player.js";
         const createButton = document.getElementById("createButton");
+        const autoButton = document.getElementById("autoButton");
         const playerId = getUserId();
         
         // Append player id to create button.
         if (playerId) {
             createButton.href += `?playerId=${playerId}`;
+            autoButton.href += `?playerId=${playerId}`;
         }
     </script>
 }
diff --git a/src/Aiursoft.ChessServer/Views/Shared/_Layout.cshtml b/src/Aiursoft.ChessServer/Views/Shared/_Layout.cshtml
index 9d829eb..db1616b 100644
--- a/src/Aiursoft.ChessServer/Views/Shared/_Layout.cshtml
+++ b/src/Aiursoft.ChessServer/Views/Shared/_Layout.cshtml
@@ -59,11 +59,12 @@
         </a>
     </div>
 </footer>
-
-<script type="module" src="~/node_modules/jquery/dist/jquery.min.js" defer></script>
-<script type="module" src="~/node_modules/bootstrap/dist/js/bootstrap.bundle.min.js" defer></script>
-<script type="module" src="~/node_modules/@@chrisoakman/chessboardjs/dist/chessboard-1.0.0.min.js" defer></script>
-<script type="module" src="~/scripts/layout.js" defer></script>
+<script src="~/node_modules/jquery/dist/jquery.min.js"></script>
+<script src="~/node_modules/jquery-validation/dist/jquery.validate.min.js"></script>
+<script src="~/node_modules/jquery-validation-unobtrusive/dist/jquery.validate.unobtrusive.min.js"></script>
+<script src="~/node_modules/bootstrap/dist/js/bootstrap.bundle.min.js"></script>
+<script src="~/node_modules/@@chrisoakman/chessboardjs/dist/chessboard-1.0.0.min.js"></script>
+<script type="module" src="~/scripts/layout.js"></script>
 @(await RenderSectionAsync("scripts", false))
 </body>
 
diff --git a/src/Aiursoft.ChessServer/wwwroot/package.json b/src/Aiursoft.ChessServer/wwwroot/package.json
index c8a6a86..eaf89c8 100644
--- a/src/Aiursoft.ChessServer/wwwroot/package.json
+++ b/src/Aiursoft.ChessServer/wwwroot/package.json
@@ -8,7 +8,8 @@
     "@aiursoft/autodark.js": "^1.2.0",
     "@chrisoakman/chessboardjs": "^1.0.0",
     "chess.js": "^1.0.0-beta.6",
+    "clipboard": "^2.0.11",
     "jquery-validation": "^1.19.5",
     "jquery-validation-unobtrusive": "^3.2.12"
   }
-}
\ No newline at end of file
+}