# VulkanAnimated

A live HUD demo: three `Observable<float>`s drive `ProgressBar`s, three
`Observable<std::string>`s drive `Text` labels, and an FPS readout in
the corner ticks every frame. Everything updates from a single
`onUpdate` listener — no `Invalidate()` / `Redraw()` calls.

## What it shows

- **`Observable<T>` data flow**: change a value in `onUpdate`, the
  next frame's `RebuildFrame` re-emits the draw list with the new value
  automatically. No tree rebuild.
- **`ProgressBar::bindValue(obs, lo, hi)`** — the bar fill normalises the
  observable's current value into 0..1 each frame.
- **`Text::bind(observable)`** — the displayed string is sourced from
  the observable each frame, replacing any baked-in runs.
- **Composition pattern**: a small lambda helper builds one HP/MP-style
  row (`Text` + `ProgressBar` inside an `HStack`) given the observables
  and a colour, then the row is dropped into the parent `VStack` like
  any other widget.
- **Different update rates per observable**: `health` oscillates at 0.7
  rad/s, `mana` at 1.3, `charge` advances linearly modulo 1 — visible
  proof that each observable updates independently.

## Run

```bash
cd examples/VulkanAnimated
crafter-build -r
```

You should see "Animated HUD" with three coloured bars (red HP, blue MP,
yellow Charge) all moving at different rates, with the FPS readout in
the top-right ticking once per frame.

Click `Quit` to exit.

## Notes

The whole tick handler is just:

```cpp
EventListener<FrameTime> tick(&window.onUpdate, [&](FrameTime ft){
    t += ft.delta.count();
    health = 0.5f + 0.5f * std::sin(t * 0.7f);
    mana   = std::abs(std::sin(t * 1.3f));
    charge = std::fmod(t * 0.3f, 1.0f);
    healthLabel = std::format("HP   {:>3.0f} / 100", health.Get() * 100);
    // …
});
```

That's the entire animation system. There is deliberately no
`Animation<T>` / tween primitive in the library — drive observables
from any source you like.