This recipe added two features to the animation you completed here: finding the size of the space where the Ball object could move, and adding a curve to the movement: both are very useful tools when designing animations for your apps.
In order to find the available space, we used a SafeArea widget containing a LayoutBuilder.
SafeArea is a widget that adds some padding to its child in order to avoid intrusions by the operating system, like the status bar at the top of the screen or the notch that you find on some phones. This is useful when you want to only use the available space for your app.
A LayoutBuilder allows measuring the space available in the current context, as it provides the parent’s constraints: in our example, the contraints of the SafeArea widget. A LayoutBuilder widget requires a builder in its constructor. This takes a function with the current context and the parent’s constraints.
Consider the following instructions:
body: SafeArea(child...