通常の再生が行われた後、最後のフレームのアニメーションが再生され続けることになり再生が停止することはありません
When playing backwards it will reach the first frame and will keep playing that. This is useful for additive animations, which should never be stopped when they reach the maximum. See Also: AnimationState.wrapMode, AnimationState.time, AnimationState.speed properties.