Anchor presets control how elements resize with parent:
- Stretch-Stretch: Element fills parent (full-screen backgrounds)
- Center-Center: Fixed size at center (popup dialogs)
- Bottom-Left: Fixed corner position (minimap)
- Top-Stretch: Stretches horizontally, fixed at top (nav bar)

using UnityEngine.UI;
using TMPro;

[SerializeField] Button startButton;
[SerializeField] TMP_InputField nameField;
[SerializeField] Slider volumeSlider;

void OnEnable()
{
    startButton.onClick.AddListener(OnStartClicked);
    nameField.onEndEdit.AddListener(OnNameChanged);
    volumeSlider.onValueChanged.AddListener(OnVolumeChanged);
}

void OnDisable()
{
    startButton.onClick.RemoveListener(OnStartClicked);
    nameField.onEndEdit.RemoveListener(OnNameChanged);
    volumeSlider.onValueChanged.RemoveListener(OnVolumeChanged);
}

UI Toolkit Stack:
  UXML  -- Structure (like HTML)
  USS   -- Styling (like CSS)
  C#    -- Logic (like JavaScript)

<ui:UXML xmlns:ui="UnityEngine.UIElements">
    <ui:VisualElement class="container">
        <ui:Label text="Player Stats" class="title" />
        <ui:ProgressBar name="health-bar" title="HP" high-value="100" />
        <ui:Button name="attack-btn" text="Attack" class="action-btn" />
        <ui:ListView name="inventory-list" />
    </ui:VisualElement>
</ui:UXML>

.container {
    flex-direction: column;
    padding: 10px;
    background-color: rgba(0, 0, 0, 0.8);
    border-radius: 8px;
}

.title {
    font-size: 24px;
    color: white;
    -unity-font-style: bold;
    margin-bottom: 10px;
}

.action-btn {
    height: 40px;
    background-color: #4CAF50;
    color: white;
    border-radius: 4px;
    transition-duration: 0.2s;
}

.action-btn:hover {
    background-color: #66BB6A;
    scale: 1.05 1.05;
}

[RequireComponent(typeof(UIDocument))]
public class StatsUI : MonoBehaviour
{
    void OnEnable()
    {
        var root = GetComponent<UIDocument>().rootVisualElement;
        var healthBar = root.Q<ProgressBar>("health-bar");
        var attackBtn = root.Q<Button>("attack-btn");
        var inventory = root.Q<ListView>("inventory-list");

        attackBtn.RegisterCallback<ClickEvent>(OnAttack);
        healthBar.value = player.Health;

        // ListView binding
        inventory.makeItem = () => new Label();
        inventory.bindItem = (element, index) =>
            ((Label)element).text = items[index].Name;
        inventory.itemsSource = items;
    }
}

// Runtime data binding with [CreateProperty] and INotifyBindablePropertyChanged
public class PlayerData : INotifyBindablePropertyChanged
{
    public event EventHandler<BindablePropertyChangedEventArgs> propertyChanged;
    private int _health;

    [CreateProperty]
    public int Health
    {
        get => _health;
        set { _health = value; Notify(); }
    }
    void Notify([CallerMemberName] string prop = "")
        => propertyChanged?.Invoke(this, new BindablePropertyChangedEventArgs(prop));
}