Flutter Animation Deep Dive — AnimationController, Custom Tweens, and Physics Simulations Flutter's animation system divides into two layers: implicit (value-driven, automatic) and explicit (controller-driven, precise). Knowing when to use each — and how to compose them — separates polished apps from janky ones. Implicit Animations: Let the Framework Drive AnimatedContainer ( duration: const Duration ( milliseconds: 400 ), curve: Curves . easeOutCubic , width: _expanded ? 300 : 100 , height: _expanded ? 200 : 60 , decoration: BoxDecoration ( color: _expanded ? Colors . indigo : Colors . indigo . shade200 , borderRadius: BorderRadius . circular ( _expanded ? 16 : 8 ), ), child: const Center ( child: Text ( 'Tap me' )), ) Enter fullscreen mode Exit fullscreen mode Flutter ships 20+ animated widgets ( AnimatedSwitcher , AnimatedOpacity , AnimatedPadding , …). Prefer them. Reach for AnimationController only when implicit widgets can't express what you need.…