Flutter Animations Master
https://api.flutter.dev/flutter/animation/Curves-class.html
주어진 애니메이션에 의해 구동되지만 이 오브젝트에 의해 결정된 값을 취하는 새 애니메이션을 반환합니다.
기본적으로 부모 값에 평가 메서드를 자동으로 적용하는 애니메이션을 반환합니다.
https://api.flutter.dev/flutter/animation/Animatable/animate.html
Returns the interpolated value for the current value of the given animation.
This method returns begin and end when the animation values are 0.0 or 1.0, respectively.
https://api.flutter.dev/flutter/animation/Tween/transform.html
90 degrees * (π radians / 180 degrees) = 0.5π radians
The angle argument must not be null. It gives the rotation in clockwise radians.
https://api.flutter.dev/flutter/widgets/Transform/Transform.rotate.html