// GameObject 기반 계층 구조
Canvas (GameObject)
  └─ Panel (GameObject + RectTransform)
       └─ Button (GameObject + Button Component)
            └─ Text (GameObject + Text Component)

// 모든 UI 요소 = GameObject
// RectTransform으로 위치/크기 제어
// MonoBehaviour 컴포넌트로 로직 추가

// Visual Element 기반 가상 트리
UIDocument (MonoBehaviour)
  └─ VisualElement (Virtual)
       └─ Button (Virtual)
            └─ Label (Virtual)

// GameObject 없음 → 메모리/CPU 절약
// USS로 스타일 제어
// C# 스크립트로 이벤트 처리

// 예시 구조
Game Scene
├─ UI Toolkit (UIDocument)
│   ├─ HUD (체력, 스태미나 바)
│   ├─ 인벤토리 시스템
│   └─ 메뉴 시스템
│
└─ uGUI (Canvas - World Space)
    ├─ NPC 위 이름표
    ├─ 데미지 숫자 (파티클)
    └─ 월드 공간 인터랙션 UI

using UnityEngine.UIElements;

public class MyUI : MonoBehaviour
{
    private void Start()
    {
        var root: VisualElement = GetComponent<UIDocument>().rootVisualElement;
        
        // VisualElement 생성
        var container: VisualElement = new VisualElement();
        [container.name](http://container.name) = "my-container";
        container.AddToClassList("container");
        
        // 자식 추가
        var label: Label = new Label("자식 요소");
        container.Add(label);
        
        // 루트에 추가
        root.Add(container);
    }
}

// 텍스트
Label label = new Label("텍스트");

// 버튼
Button button = new Button(() => Debug.Log("클릭!"));
button.text = "클릭하세요";

// 텍스트 입력
TextField textField = new TextField("라벨");
textField.value = "초기값";

// 이미지 (VisualElement + background-image)
VisualElement image = new VisualElement();
[image.style](http://image.style).backgroundImage = new StyleBackground(myTexture);

// 토글
Toggle toggle = new Toggle("체크박스");
toggle.value = true;

// 슬라이더
Slider slider = new Slider("볼륨", 0, 100);
slider.value = 50;

// 드롭다운
DropdownField dropdown = new DropdownField("옵션", new List<string> { "A", "B", "C" }, 0);

// 스크롤 뷰
ScrollView scrollView = new ScrollView();
scrollView.Add(new Label("스크롤 콘텐츠"));

// Foldout (접을 수 있는 영역)
Foldout foldout = new Foldout();
foldout.text = "펼치기/접기";
foldout.Add(new Label("숨겨진 콘텐츠"));

// GroupBox (그룹화)
GroupBox groupBox = new GroupBox("그룹");
groupBox.Add(new Label("그룹 내용"));

using UnityEngine.UIElements;

public class UIController : MonoBehaviour
{
    [SerializeField] private UIDocument _uiDocument;
    
    private void Start()
    {
        var root: VisualElement = _uiDocument.rootVisualElement;
        
        // name으로 찾기 (권장)
        Button submitButton = root.Q<Button>("submit-button");
        submitButton.clicked += OnSubmitClicked;
        
        // class로 찾기
        var primaryButtons: UQueryBuilder<Button> = root.Query<Button>(className: "primary-button");
        primaryButtons.ForEach(btn => [btn.style](http://btn.style).backgroundColor = [Color.blue](http://Color.blue));
        
        // 타입으로 모든 요소 찾기
        List<Label> allLabels = root.Query<Label>().ToList();
        
        // 자식 직접 접근
        VisualElement firstChild = root[0]; // 첫 번째 자식
        int childCount = root.childCount;
    }
    
    private void OnSubmitClicked()
    {
        Debug.Log($"제출 버튼 클릭!");
    }
}

// 부모 접근
VisualElement parent = myElement.parent;

// 자식 순회
foreach (VisualElement child in myElement.Children())
{
    Debug.Log($"자식: {[child.name](http://child.name)}");
}

// 형제 접근
int index = myElement.parent.IndexOf(myElement);
VisualElement nextSibling = myElement.parent[index + 1];

// 조상 찾기
VisualElement ancestor = myElement.GetFirstAncestorOfType<ScrollView>();

public class InventoryUI : MonoBehaviour
{
    [SerializeField] private UIDocument _uiDocument;
    private VisualElement _itemContainer;
    
    private void Start()
    {
        var root: VisualElement = _uiDocument.rootVisualElement;
        _itemContainer = root.Q<VisualElement>("item-container");
        
        // 아이템 10개 생성
        for (int i = 0; i < 10; i++)
        {
            CreateItemSlot(i);
        }
    }
    
    private void CreateItemSlot(int index: int)
    {
        // 슬롯 컨테이너
        var slot: VisualElement = new VisualElement();
        [slot.name](http://slot.name) = $"item-slot-{index}";
        slot.AddToClassList("item-slot");
        
        // 아이콘
        var icon: VisualElement = new VisualElement();
        [icon.name](http://icon.name) = "icon";
        icon.AddToClassList("item-icon");
        slot.Add(icon);
        
        // 이름
        var itemName: Label = new Label($"아이템 {index + 1}");
        itemName.AddToClassList("item-name");
        slot.Add(itemName);
        
        // 수량
        var count: Label = new Label("x1");
        count.AddToClassList("item-count");
        slot.Add(count);
        
        // 클릭 이벤트
        slot.RegisterCallback<ClickEvent>(evt => OnItemClicked(index));
        
        _itemContainer.Add(slot);
    }
    
    private void OnItemClicked(int index: int)
    {
        Debug.Log($"아이템 {index} 클릭!");
    }
}

// 추가
parent.Add(child);
parent.Insert(0, child); // 특정 인덱스에 추가

// 제거
parent.Remove(child);
parent.RemoveAt(0); // 인덱스로 제거
parent.Clear(); // 모든 자식 제거

// 교체
parent.Remove(oldChild);
parent.Add(newChild);

// Display (렌더링 + 레이아웃 제외)
[element.style](http://element.style).display = DisplayStyle.None; // 숨김
[element.style](http://element.style).display = DisplayStyle.Flex; // 표시

// Visibility (렌더링만 제외, 레이아웃 유지)
[element.style](http://element.style).visibility = Visibility.Hidden;
[element.style](http://element.style).visibility = Visibility.Visible;

// USS 클래스 토글
element.AddToClassList("hidden"); // .hidden { display: none; }
element.RemoveFromClassList("hidden");
element.ToggleInClassList("hidden");

using UnityEngine;
using UnityEngine.UIElements;

public class UIController : MonoBehaviour
{
    [SerializeField] private UIDocument _uiDocument;
    private VisualElement _root;
    
    private void Awake()
    {
        // rootVisualElement 가져오기
        _root = _uiDocument.rootVisualElement;
    }
}

using UnityEngine.UIElements;

public class LoginController : MonoBehaviour
{
    private TextField _usernameField;
    private TextField _passwordField;
    private Button _loginButton;
    private Label _errorMessage;
    
    private void Start()
    {
        var root: VisualElement = GetComponent<UIDocument>().rootVisualElement;
        
        // name으로 요소 찾기
        _usernameField = root.Q<TextField>("username-field");
        _passwordField = root.Q<TextField>("password-field");
        _loginButton = root.Q<Button>("login-button");
        _errorMessage = root.Q<Label>("error-message");
        
        // null 체크
        if (_loginButton == null)
        {
            Debug.LogError($"login-button을 찾을 수 없습니다!");
            return;
        }
    }
}

// class로 모든 버튼 찾기
var menuButtons: UQueryBuilder<Button> = root.Query<Button>(className: "menu-button");

// ForEach로 순회
menuButtons.ForEach(button =>
{
    button.clicked += () => OnMenuButtonClicked(button.text);
});

// 리스트로 변환
List<Button> buttonList = menuButtons.ToList();

// 개수 확인
int count = menuButtons.ToList().Count;

private void Start()
{
    var root: VisualElement = GetComponent<UIDocument>().rootVisualElement;
    
    // 방법 1: clicked 이벤트
    Button submitButton = root.Q<Button>("submit-button");
    submitButton.clicked += OnSubmitClicked;
    
    // 방법 2: 람다
    root.Q<Button>("cancel-button").clicked += () =>
    {
        Debug.Log($"취소 클릭!");
    };
}

private void OnSubmitClicked()
{
    Debug.Log($"제출 버튼 클릭!");
}

private void OnDestroy()
{
    // 이벤트 해제 (메모리 누수 방지)
    Button submitButton = GetComponent<UIDocument>().rootVisualElement.Q<Button>("submit-button");
    if (submitButton != null)
    {
        submitButton.clicked -= OnSubmitClicked;
    }
}

private void Start()
{
    var root: VisualElement = GetComponent<UIDocument>().rootVisualElement;
    
    TextField nameField = root.Q<TextField>("name-field");
    
    // 방법 1: RegisterValueChangedCallback
    nameField.RegisterValueChangedCallback(evt =>
    {
        string oldValue = evt.previousValue;
        string newValue = evt.newValue;
        Debug.Log($"이름 변경: {oldValue} -> {newValue}");
    });
    
    // 방법 2: RegisterCallback (더 저수준)
    nameField.RegisterCallback<ChangeEvent<string>>(evt =>
    {
        Debug.Log($"새 값: {evt.newValue}");
    });
}

private void Start()
{
    var root: VisualElement = GetComponent<UIDocument>().rootVisualElement;
    
    // Toggle
    Toggle muteToggle = root.Q<Toggle>("mute-toggle");
    muteToggle.RegisterValueChangedCallback(evt =>
    {
        bool isMuted = evt.newValue;
        AudioListener.volume = isMuted ? 0f : 1f;
    });
    
    // Slider
    Slider volumeSlider = root.Q<Slider>("volume-slider");
    volumeSlider.RegisterValueChangedCallback(evt =>
    {
        float volume = evt.newValue;
        AudioListener.volume = volume / 100f;
    });
    
    // DropdownField
    DropdownField difficultyDropdown = root.Q<DropdownField>("difficulty-dropdown");
    difficultyDropdown.RegisterValueChangedCallback(evt =>
    {
        string difficulty = evt.newValue;
        Debug.Log($"난이도: {difficulty}");
    });
}

// 색상 변경
[element.style](http://element.style).backgroundColor = new StyleColor([Color.red](http://Color.red));
[element.style](http://element.style).color = new StyleColor(Color.white);

// 크기 변경
[element.style](http://element.style).width = new StyleLength(200f); // px
[element.style](http://element.style).height = new StyleLength(Length.Percent(50)); // %

// 여백
[element.style](http://element.style).marginTop = new StyleLength(10f);
[element.style](http://element.style).paddingLeft = new StyleLength(20f);

// 테두리
[element.style](http://element.style).borderTopWidth = new StyleFloat(2f);
[element.style](http://element.style).borderTopColor = new StyleColor(Color.white);
[element.style](http://element.style).borderRadius = new StyleLength(10f);

// 표시/숨김
[element.style](http://element.style).display = DisplayStyle.None;
[element.style](http://element.style).visibility = Visibility.Hidden;

// 배경 이미지
Texture2D texture = Resources.Load<Texture2D>("Textures/background");
[element.style](http://element.style).backgroundImage = new StyleBackground(texture);

// Transform
[element.style](http://element.style).scale = new StyleScale(new Scale(new Vector3(1.5f, 1.5f, 1f)));
[element.style](http://element.style).rotate = new StyleRotate(new Rotate(45f));

// 클래스 추가
element.AddToClassList("highlighted");

// 클래스 제거
element.RemoveFromClassList("highlighted");

// 클래스 토글
element.ToggleInClassList("highlighted");

// 클래스 존재 확인
bool hasClass = element.ClassListContains("highlighted");

// 여러 클래스 동시 적용
element.AddToClassList("card");
element.AddToClassList("active");
element.AddToClassList("highlighted");

using UnityEngine;
using UnityEngine.UIElements;
using System.Collections;

public class LoginController : MonoBehaviour
{
    [SerializeField] private UIDocument _uiDocument;
    
    private TextField _usernameField;
    private TextField _passwordField;
    private Button _loginButton;
    private Label _errorMessage;
    
    private void Start()
    {
        var root: VisualElement = _uiDocument.rootVisualElement;
        
        // 요소 찾기
        _usernameField = root.Q<TextField>("username-field");
        _passwordField = root.Q<TextField>("password-field");
        _loginButton = root.Q<Button>("login-button");
        _errorMessage = root.Q<Label>("error-message");
        
        // 이벤트 등록
        _loginButton.clicked += OnLoginClicked;
        
        // Enter 키 로그인
        _passwordField.RegisterCallback<KeyDownEvent>(evt =>
        {
            if (evt.keyCode == KeyCode.Return)
            {
                OnLoginClicked();
            }
        });
        
        // 초기 에러 메시지 숨김
        _[errorMessage.style](http://errorMessage.style).display = DisplayStyle.None;
    }
    
    private void OnLoginClicked()
    {
        string username = _usernameField.value;
        string password = _passwordField.value;
        
        // 유효성 검사
        if (string.IsNullOrEmpty(username))
        {
            ShowError("아이디를 입력하세요");
            return;
        }
        
        if (string.IsNullOrEmpty(password))
        {
            ShowError("비밀번호를 입력하세요");
            return;
        }
        
        // 로그인 처리
        StartCoroutine(LoginCoroutine(username, password));
    }
    
    private IEnumerator LoginCoroutine(string username: string, string password: string)
    {
        // 버튼 비활성화
        _loginButton.SetEnabled(false);
        _loginButton.text = "로그인 중...";
        
        // 가상의 API 호출
        yield return new WaitForSeconds(2f);
        
        // 간단한 인증 로직
        if (username == "admin" && password == "1234")
        {
            Debug.Log($"로그인 성공!");
            // 메인 화면으로 이동
        }
        else
        {
            ShowError("아이디 또는 비밀번호가 잘못되었습니다");
            
            // 버튼 재활성화
            _loginButton.SetEnabled(true);
            _loginButton.text = "로그인";
        }
    }
    
    private void ShowError(string message: string)
    {
        _errorMessage.text = message;
        _[errorMessage.style](http://errorMessage.style).display = DisplayStyle.Flex;
        
        // 3초 후 자동 숨김
        StartCoroutine(HideErrorAfterDelay(3f));
    }
    
    private IEnumerator HideErrorAfterDelay(float delay: float)
    {
        yield return new WaitForSeconds(delay);
        _[errorMessage.style](http://errorMessage.style).display = DisplayStyle.None;
    }
    
    private void OnDestroy()
    {
        // 이벤트 해제
        if (_loginButton != null)
        {
            _loginButton.clicked -= OnLoginClicked;
        }
    }
}

using UnityEngine;

public class PlayerData : MonoBehaviour
{
    public string playerName = "Player";
    public int level = 1;
    public float health = 100f;
    public bool isAlive = true;
}

using UnityEditor;
using UnityEngine.UIElements;

[CustomEditor(typeof(PlayerData))]
public class PlayerDataEditor : Editor
{
    public override VisualElement CreateInspectorGUI()
    {
        // 루트 컨테이너
        var root: VisualElement = new VisualElement();
        
        // TextField 생성 및 바인딩
        var nameField: TextField = new TextField("Player Name");
        nameField.bindingPath = "playerName"; // 프로퍼티명과 동일
        root.Add(nameField);
        
        // IntegerField 바인딩
        var levelField: IntegerField = new IntegerField("Level");
        levelField.bindingPath = "level";
        root.Add(levelField);
        
        // FloatField 바인딩
        var healthField: FloatField = new FloatField("Health");
        healthField.bindingPath = "health";
        root.Add(healthField);
        
        // Toggle 바인딩
        var aliveToggle: Toggle = new Toggle("Is Alive");
        aliveToggle.bindingPath = "isAlive";
        root.Add(aliveToggle);
        
        return root;
    }
}

using UnityEditor;
using UnityEngine.UIElements;

[CustomEditor(typeof(PlayerData))]
public class PlayerDataEditor : Editor
{
    [SerializeField] private VisualTreeAsset _uxml;
    
    public override VisualElement CreateInspectorGUI()
    {
        var root: VisualElement = new VisualElement();
        
        // UXML 로드
        _uxml.CloneTree(root);
        
        // 자동 바인딩 (반드시 호출!)
        return root;
    }
}

using UnityEngine.UIElements;

public class HealthBar : VisualElement
{
    public new class UxmlFactory : UxmlFactory<HealthBar, UxmlTraits> { }
    
    public new class UxmlTraits : VisualElement.UxmlTraits
    {
        UxmlFloatAttributeDescription _maxHealth = new UxmlFloatAttributeDescription 
        { 
            name = "max-health", 
            defaultValue = 100f 
        };
        
        UxmlFloatAttributeDescription _currentHealth = new UxmlFloatAttributeDescription 
        { 
            name = "current-health", 
            defaultValue = 100f 
        };
        
        public override void Init(VisualElement ve: VisualElement, IUxmlAttributes bag: IUxmlAttributes, CreationContext cc: CreationContext)
        {
            base.Init(ve, bag, cc);
            var healthBar: HealthBar = ve as HealthBar;
            
            healthBar.MaxHealth = _maxHealth.GetValueFromBag(bag, cc);
            healthBar.CurrentHealth = _currentHealth.GetValueFromBag(bag, cc);
        }
    }
    
    private VisualElement _fillBar;
    private Label _label;
    
    private float _maxHealth;
    private float _currentHealth;
    
    public float MaxHealth
    {
        get => _maxHealth;
        set
        {
            _maxHealth = value;
            UpdateDisplay();
        }
    }
    
    public float CurrentHealth
    {
        get => _currentHealth;
        set
        {
            _currentHealth = value;
            UpdateDisplay();
        }
    }
    
    public HealthBar()
    {
        // 컨테이너
        AddToClassList("health-bar");
        
        // 배경
        var background: VisualElement = new VisualElement();
        background.AddToClassList("health-bar-background");
        Add(background);
        
        // 채우기 바
        _fillBar = new VisualElement();
        _fillBar.AddToClassList("health-bar-fill");
        background.Add(_fillBar);
        
        // 라벨
        _label = new Label();
        _label.AddToClassList("health-bar-label");
        Add(_label);
    }
    
    private void UpdateDisplay()
    {
        float percentage = _currentHealth / _maxHealth;
        _[fillBar.style](http://fillBar.style).width = Length.Percent(percentage * 100);
        _label.text = $"{_currentHealth:F0} / {_maxHealth:F0}";
        
        // 색상 변경
        if (percentage > 0.5f)
        {
            _[fillBar.style](http://fillBar.style).backgroundColor = [Color.green](http://Color.green);
        }
        else if (percentage > 0.2f)
        {
            _[fillBar.style](http://fillBar.style).backgroundColor = Color.yellow;
        }
        else
        {
            _[fillBar.style](http://fillBar.style).backgroundColor = [Color.red](http://Color.red);
        }
    }
}

var healthBar: HealthBar = new HealthBar();
healthBar.MaxHealth = 100f;
healthBar.CurrentHealth = 75f;
root.Add(healthBar);

// 체력 감소
healthBar.CurrentHealth -= 25f;

using [Unity.Properties](http://Unity.Properties); // Package Manager에서 설치 필요
using UnityEngine;
using UnityEngine.UIElements;

[System.Serializable]
public class PlayerStats
{
    [CreateProperty]
    public string Name { get; set; } = "Player";
    
    [CreateProperty]
    public int Level { get; set; } = 1;
    
    [CreateProperty]
    public float Health { get; set; } = 100f;
}

public class PlayerUI : MonoBehaviour
{
    [SerializeField] private UIDocument _uiDocument;
    private PlayerStats _playerStats = new PlayerStats();
    
    private void Start()
    {
        var root: VisualElement = _uiDocument.rootVisualElement;
        
        // 바인딩 설정
        var nameLabel: Label = root.Q<Label>("player-name");
        nameLabel.dataSource = _playerStats;
        nameLabel.SetBinding("text", new DataBinding { dataSourcePath = new PropertyPath("Name") });
        
        var levelLabel: Label = root.Q<Label>("player-level");
        levelLabel.dataSource = _playerStats;
        levelLabel.SetBinding("text", new DataBinding { dataSourcePath = new PropertyPath("Level") });
        
        // 데이터 변경 시 자동 업데이트
        StartCoroutine(UpdateStatsRoutine());
    }
    
    private IEnumerator UpdateStatsRoutine()
    {
        while (true)
        {
            yield return new WaitForSeconds(1f);
            _playerStats.Level++;
            _[playerStats.Health](http://playerStats.Health) -= 5f;
        }
    }
}

using UnityEngine;
using UnityEngine.UIElements;

public class CustomButton : VisualElement
{
    // UI Builder에서 사용 가능하게 하려면 필수
    public new class UxmlFactory : UxmlFactory<CustomButton, UxmlTraits> { }
    
    // UXML 속성 정의
    public new class UxmlTraits : VisualElement.UxmlTraits
    {
        UxmlStringAttributeDescription _text = new UxmlStringAttributeDescription 
        { 
            name = "text", 
            defaultValue = "Button" 
        };
        
        public override void Init(VisualElement ve: VisualElement, IUxmlAttributes bag: IUxmlAttributes, CreationContext cc: CreationContext)
        {
            base.Init(ve, bag, cc);
            var button: CustomButton = ve as CustomButton;
            button.Text = _text.GetValueFromBag(bag, cc);
        }
    }
    
    // 내부 요소
    private Label _label;
    private VisualElement _icon;
    
    // 프로퍼티
    private string _text;
    public string Text
    {
        get => _text;
        set
        {
            _text = value;
            _label.text = value;
        }
    }
    
    // 이벤트
    public event System.Action Clicked;
    
    public CustomButton()
    {
        // 스타일 클래스
        AddToClassList("custom-button");
        
        // 아이콘
        _icon = new VisualElement();
        _icon.AddToClassList("custom-button-icon");
        Add(_icon);
        
        // 라벨
        _label = new Label();
        _label.AddToClassList("custom-button-label");
        Add(_label);
        
        // 클릭 이벤트 등록
        RegisterCallback<ClickEvent>(OnClick);
    }
    
    private void OnClick(ClickEvent evt: ClickEvent)
    {
        Clicked?.Invoke();
    }
    
    // 아이콘 설정
    public void SetIcon(Texture2D texture: Texture2D)
    {
        _[icon.style](http://icon.style).backgroundImage = new StyleBackground(texture);
    }
}

var customButton: CustomButton = new CustomButton();
customButton.Text = "클릭하세요";
customButton.SetIcon(myIconTexture);
customButton.Clicked += () =>
{
    Debug.Log($"커스텀 버튼 클릭!");
};
root.Add(customButton);

using UnityEngine;
using UnityEngine.UIElements;

public class ProgressBar : VisualElement
{
    public new class UxmlFactory : UxmlFactory<ProgressBar, UxmlTraits> { }
    
    public new class UxmlTraits : VisualElement.UxmlTraits
    {
        UxmlFloatAttributeDescription _min = new UxmlFloatAttributeDescription 
        { 
            name = "min-value", 
            defaultValue = 0f 
        };
        
        UxmlFloatAttributeDescription _max = new UxmlFloatAttributeDescription 
        { 
            name = "max-value", 
            defaultValue = 100f 
        };
        
        UxmlFloatAttributeDescription _value = new UxmlFloatAttributeDescription 
        { 
            name = "value", 
            defaultValue = 0f 
        };
        
        UxmlStringAttributeDescription _label = new UxmlStringAttributeDescription 
        { 
            name = "label", 
            defaultValue = "" 
        };
        
        public override void Init(VisualElement ve: VisualElement, IUxmlAttributes bag: IUxmlAttributes, CreationContext cc: CreationContext)
        {
            base.Init(ve, bag, cc);
            var bar: ProgressBar = ve as ProgressBar;
            
            bar.MinValue = _min.GetValueFromBag(bag, cc);
            bar.MaxValue = _max.GetValueFromBag(bag, cc);
            bar.Value = _value.GetValueFromBag(bag, cc);
            bar.Label = _label.GetValueFromBag(bag, cc);
        }
    }
    
    private VisualElement _background;
    private VisualElement _fill;
    private Label _labelElement;
    private Label _percentElement;
    
    private float _minValue = 0f;
    private float _maxValue = 100f;
    private float _value = 0f;
    private string _label = "";
    
    public float MinValue
    {
        get => _minValue;
        set
        {
            _minValue = value;
            UpdateDisplay();
        }
    }
    
    public float MaxValue
    {
        get => _maxValue;
        set
        {
            _maxValue = value;
            UpdateDisplay();
        }
    }
    
    public float Value
    {
        get => _value;
        set
        {
            _value = Mathf.Clamp(value, _minValue, _maxValue);
            UpdateDisplay();
        }
    }
    
    public string Label
    {
        get => _label;
        set
        {
            _label = value;
            _labelElement.text = value;
            _[labelElement.style](http://labelElement.style).display = string.IsNullOrEmpty(value) ? DisplayStyle.None : DisplayStyle.Flex;
        }
    }
    
    public ProgressBar()
    {
        AddToClassList("progress-bar");
        
        // 라벨
        _labelElement = new Label();
        _labelElement.AddToClassList("progress-bar-label");
        Add(_labelElement);
        
        // 배경
        _background = new VisualElement();
        _background.AddToClassList("progress-bar-background");
        Add(_background);
        
        // 채우기
        _fill = new VisualElement();
        _fill.AddToClassList("progress-bar-fill");
        _background.Add(_fill);
        
        // 퍼센트
        _percentElement = new Label();
        _percentElement.AddToClassList("progress-bar-percent");
        _background.Add(_percentElement);
        
        UpdateDisplay();
    }
    
    private void UpdateDisplay()
    {
        float range = _maxValue - _minValue;
        float normalized = (range > 0) ? (_value - _minValue) / range : 0f;
        float percent = normalized * 100f;
        
        // 채우기 너비
        _[fill.style](http://fill.style).width = Length.Percent(percent);
        
        // 퍼센트 표시
        _percentElement.text = $"{percent:F0}%";
        
        // 색상 그라데이션
        Color fillColor = Color.Lerp([Color.red](http://Color.red), [Color.green](http://Color.green), normalized);
        _[fill.style](http://fill.style).backgroundColor = fillColor;
    }
    
    // 부드럽게 증가
    public void AnimateToValue(float targetValue: float, float duration: float)
    {
        VisualElement ve = this;
        ve.schedule.Execute(() =>
        {
            float current = Value;
            float target = Mathf.Clamp(targetValue, _minValue, _maxValue);
            float step = (target - current) * Time.deltaTime / duration;
            
            Value = current + step;
            
            if (Mathf.Abs(target - current) < 0.1f)
            {
                Value = target;
            }
        }).Every(16); // ~60 FPS
    }
}

// UXML
<ProgressBar label="로딩" min-value="0" max-value="100" value="0" />

// C#
var progressBar: ProgressBar = new ProgressBar();
progressBar.Label = "로딩";
progressBar.MinValue = 0f;
progressBar.MaxValue = 100f;
progressBar.Value = 0f;
root.Add(progressBar);

// 진행률 업데이트
progressBar.AnimateToValue(100f, 3f); // 3초동안 100%까지

using UnityEngine;
using UnityEngine.UIElements;

public class ResponsiveUI : MonoBehaviour
{
    [SerializeField] private UIDocument _uiDocument;
    private VisualElement _container;
    
    private void Start()
    {
        var root = _uiDocument.rootVisualElement;
        _container = root.Q<VisualElement>("container");
        
        UpdateLayout();
    }
    
    private void Update()
    {
        // 화면 크기 변경 감지
        if (Screen.width != _lastWidth || Screen.height != _lastHeight)
        {
            UpdateLayout();
            _lastWidth = Screen.width;
            _lastHeight = Screen.height;
        }
    }
    
    private int _lastWidth;
    private int _lastHeight;
    
    private void UpdateLayout()
    {
        _container.RemoveFromClassList("container-mobile");
        _container.RemoveFromClassList("container-tablet");
        _container.RemoveFromClassList("container-desktop");
        
        if (Screen.width < 768)
        {
            _container.AddToClassList("container-mobile");
        }
        else if (Screen.width < 1024)
        {
            _container.AddToClassList("container-tablet");
        }
        else
        {
            _container.AddToClassList("container-desktop");
        }
    }
}

using UnityEngine.UIElements;

public class TransitionController : MonoBehaviour
{
    private void Start()
    {
        var root = GetComponent<UIDocument>().rootVisualElement;
        var element = root.Q<VisualElement>("animated-element");
        
        // Transition 시작 이벤트
        element.RegisterCallback<TransitionStartEvent>(evt =>
        {
            Debug.Log($"Transition 시작: {evt.stylePropertyNames}");
        });
        
        // Transition 종료 이벤트
        element.RegisterCallback<TransitionEndEvent>(evt =>
        {
            Debug.Log($"Transition 종료: {evt.stylePropertyNames}");
        });
    }
}

// 페이드 인 애니메이션
public void FadeIn(VisualElement element, float duration)
{
    [element.style](http://element.style).opacity = 0;
    
    float elapsed = 0f;
    element.schedule.Execute(() =>
    {
        elapsed += 0.016f; // ~60 FPS
        float progress = Mathf.Clamp01(elapsed / duration);
        [element.style](http://element.style).opacity = progress;
        
        if (progress >= 1f)
        {
            return; // 종료
        }
    }).Every(16); // 16ms = 60 FPS
}

// 슬라이드 인 애니메이션
public void SlideIn(VisualElement element, float duration)
{
    [element.style](http://element.style).translate = new Translate(0, -100, 0);
    
    float elapsed = 0f;
    element.schedule.Execute(() =>
    {
        elapsed += 0.016f;
        float progress = Mathf.Clamp01(elapsed / duration);
        float y = Mathf.Lerp(-100f, 0f, progress);
        [element.style](http://element.style).translate = new Translate(0, y, 0);
        
        if (progress >= 1f)
        {
            return;
        }
    }).Every(16);
}

using System.Collections;

public IEnumerator PulseAnimation(VisualElement element)
{
    while (true)
    {
        // 확대
        float elapsed = 0f;
        while (elapsed < 0.5f)
        {
            elapsed += Time.deltaTime;
            float scale = Mathf.Lerp(1f, 1.2f, elapsed / 0.5f);
            [element.style](http://element.style).scale = new Scale(new Vector3(scale, scale, 1f));
            yield return null;
        }
        
        // 축소
        elapsed = 0f;
        while (elapsed < 0.5f)
        {
            elapsed += Time.deltaTime;
            float scale = Mathf.Lerp(1.2f, 1f, elapsed / 0.5f);
            [element.style](http://element.style).scale = new Scale(new Vector3(scale, scale, 1f));
            yield return null;
        }
    }
}

using UnityEngine;
using UnityEngine.UIElements;

public class GameHUD : MonoBehaviour
{
    [SerializeField] private UIDocument _uiDocument;
    
    private Label _scoreLabel;
    private Label _timerLabel;
    private VisualElement _healthBar;
    private VisualElement _healthFill;
    
    private int _score = 0;
    private float _health = 100f;
    private float _gameTime = 0f;
    
    private void Start()
    {
        var root = _uiDocument.rootVisualElement;
        
        _scoreLabel = root.Q<Label>("score-label");
        _timerLabel = root.Q<Label>("timer-label");
        _healthBar = root.Q<VisualElement>("health-bar");
        _healthFill = root.Q<VisualElement>("health-fill");
        
        UpdateUI();
    }
    
    private void Update()
    {
        _gameTime += Time.deltaTime;
        UpdateTimer();
    }
    
    public void AddScore(int points)
    {
        _score += points;
        _scoreLabel.text = $"점수: {_score}";
        
        // 점수 증가 효과
        StartCoroutine(ScorePopAnimation());
    }
    
    public void TakeDamage(float damage)
    {
        _health = Mathf.Max(0, _health - damage);
        UpdateHealth();
        
        if (_health <= 0)
        {
            OnGameOver();
        }
    }
    
    private void UpdateHealth()
    {
        float percentage = _health / 100f;
        _[healthFill.style](http://healthFill.style).width = Length.Percent(percentage * 100);
        
        // 색상 변경
        if (percentage > 0.5f)
            _[healthFill.style](http://healthFill.style).backgroundColor = [Color.green](http://Color.green);
        else if (percentage > 0.2f)
            _[healthFill.style](http://healthFill.style).backgroundColor = Color.yellow;
        else
            _[healthFill.style](http://healthFill.style).backgroundColor = [Color.red](http://Color.red);
    }
    
    private void UpdateTimer()
    {
        int minutes = Mathf.FloorToInt(_gameTime / 60f);
        int seconds = Mathf.FloorToInt(_gameTime % 60f);
        _timerLabel.text = $"{minutes:00}:{seconds:00}";
    }
    
    private IEnumerator ScorePopAnimation()
    {
        _[scoreLabel.style](http://scoreLabel.style).scale = new Scale([Vector3.one](http://Vector3.one) * 1.3f);
        yield return new WaitForSeconds(0.2f);
        _[scoreLabel.style](http://scoreLabel.style).scale = new Scale([Vector3.one](http://Vector3.one));
    }
    
    private void OnGameOver()
    {
        Debug.Log($"게임 오버! 최종 점수: {_score}");
    }
    
    private void UpdateUI()
    {
        _scoreLabel.text = $"점수: {_score}";
        UpdateHealth();
        UpdateTimer();
    }
}

using UnityEngine;
using UnityEngine.UIElements;
using System.Collections.Generic;

public class InventorySystem : MonoBehaviour
{
    [SerializeField] private UIDocument _uiDocument;
    [SerializeField] private VisualTreeAsset _itemSlotTemplate;
    
    private VisualElement _inventoryGrid;
    private List<ItemData> _items = new List<ItemData>();
    
    private void Start()
    {
        var root = _uiDocument.rootVisualElement;
        _inventoryGrid = root.Q<VisualElement>("inventory-grid");
        
        // 30개 슬롯 생성
        for (int i = 0; i < 30; i++)
        {
            CreateItemSlot(i);
        }
        
        // 테스트 아이템 추가
        AddItem(new ItemData { name = "검", icon = null, count = 1 });
        AddItem(new ItemData { name = "포션", icon = null, count = 5 });
    }
    
    private void CreateItemSlot(int index)
    {
        var slot = _itemSlotTemplate.CloneTree();
        slot.AddToClassList("item-slot");
        [slot.name](http://slot.name) = $"slot-{index}";
        
        // 클릭 이벤트
        slot.RegisterCallback<ClickEvent>(evt =>
        {
            OnSlotClicked(index);
        });
        
        _inventoryGrid.Add(slot);
    }
    
    public void AddItem(ItemData item)
    {
        _items.Add(item);
        UpdateSlot(_items.Count - 1, item);
    }
    
    private void UpdateSlot(int index, ItemData item)
    {
        var slot = _inventoryGrid.Q<VisualElement>($"slot-{index}");
        
        var icon = slot.Q<VisualElement>("item-icon");
        var nameLabel = slot.Q<Label>("item-name");
        var countLabel = slot.Q<Label>("item-count");
        
        if (item.icon != null)
            [icon.style](http://icon.style).backgroundImage = new StyleBackground(item.icon);
        
        nameLabel.text = [item.name](http://item.name);
        countLabel.text = $"x{item.count}";
        
        slot.RemoveFromClassList("empty");
        slot.AddToClassList("filled");
    }
    
    private void OnSlotClicked(int index)
    {
        if (index < _items.Count)
        {
            Debug.Log($"아이템 사용: {_items[index].name}");
        }
    }
}

[System.Serializable]
public class ItemData
{
    public string name;
    public Texture2D icon;
    public int count;
}