# Tween

animate any property over time with easing.

```{raw} html
<a class="example-run-button" href="../demos/features_2d_tween.html">▶ Run in browser</a>

```

**Tags:** `2d` `animation` `tween`

`tween()` smoothly drives a property from its current value to a target over a
duration, optionally with an easing curve and repeats. It is a coroutine: hand it
to `start_coroutine()` and the node's lifecycle runs it. This example races a
marker along each row using a different easing function so you can see how the
curves differ; every marker covers the same distance in the same time.


## What it demonstrates

- `tween(obj, prop, target, duration, easing=...)` -- interpolate a scalar or a
  `Vec2` property (here, each marker's `position`).
- Easing functions (`ease_linear`, `ease_in_quad`, `ease_out_quad`,
  `ease_in_out_cubic`, ...) shape the motion: slow-in, slow-out, both, or none.
- `repeat` + `repeat_mode="yoyo"` to ping-pong the animation back and forth.
- `start_coroutine()` to run a tween from a node.

## Source

```{literalinclude} ../../examples/features/2d/tween.py
:language: python
:linenos:
```