# UI System

SimVX provides a set of UI controls and layout containers for building game interfaces.

## Controls

All controls inherit from `Control`, which provides rect-based layout, mouse interaction, and focus management.

### Label

```python
from simvx.core import Label

label = Label(text="Score: 0", font_size=24)
label.position = Vec2(10, 10)
root.add_child(label)
```

### Button

```python
from simvx.core import Button

btn = Button(text="Start Game")
btn.pressed.connect(start_game)
root.add_child(btn)
```

### TextEdit

```python
from simvx.core import TextEdit

edit = TextEdit(placeholder="Enter name...")
edit.text_changed.connect(lambda text: print(text))
root.add_child(edit)
```

### Slider

```python
from simvx.core import Slider

slider = Slider(min_value=0, max_value=100, value=50)
slider.value_changed.connect(lambda v: print(f"Volume: {v}"))
root.add_child(slider)
```

### ProgressBar

```python
from simvx.core import ProgressBar

bar = ProgressBar(min_value=0, max_value=100, value=75)
root.add_child(bar)
```

## Containers

Containers automatically arrange their children.

### HBoxContainer / VBoxContainer

```python
from simvx.core import HBoxContainer, VBoxContainer, Button

menu = VBoxContainer(separation=10)
menu.add_child(Button(text="New Game"))
menu.add_child(Button(text="Load Game"))
menu.add_child(Button(text="Settings"))
root.add_child(menu)
```

### GridContainer

```python
from simvx.core import GridContainer

grid = GridContainer(columns=3, h_separation=5, v_separation=5)
for i in range(9):
    grid.add_child(Button(text=str(i + 1)))
```

### MarginContainer

```python
from simvx.core import MarginContainer

margin = MarginContainer(
    margin_left=20, margin_right=20,
    margin_top=10, margin_bottom=10,
)
margin.add_child(Label(text="Padded content"))
```

## Theming

Apply consistent styling across controls:

```python
from simvx.core import Theme

theme = Theme(
    bg_color=(0.2, 0.2, 0.2, 1.0),
    fg_color=(1.0, 1.0, 1.0, 1.0),
    accent_color=(0.3, 0.6, 1.0, 1.0),
    font_size=16,
)
```

## Input Handling

UI input is routed through the `SceneTree`:

```python
tree.ui_input(mouse_pos=(100, 200), button=1, pressed=True)
tree.ui_input(key="return", pressed=True)
```

## API Reference

See {py:mod}`simvx.core.ui` for the complete UI API.