riversong-code-showcase/Source/Riversong/Game/World/RawResources/TreeFallAnimation.cs

using Cysharp.Threading.Tasks;
using UnityEngine;

namespace DanieleMarotta.RiversongCodeShowcase
{
    public class TreeFallAnimation : MonoBehaviour, IDestroyRawResourceAnimation
    {
        [SerializeField]
        private float _fallDelay;

        [SerializeField]
        private float _fallDuration = 1;

        [SerializeField]
        private AnimationCurve _fallRotationCurve = AnimationCurve.Linear(0, 0, 1, 1);

        [SerializeField]
        private float _sinkDelay = 0.5f;

        [SerializeField]
        private float _sinkDepth = 1;

        [SerializeField]
        private float _sinkSpeed = 1;

        public async UniTask PlayAsync()
        {
            await FallAsync();
            await SinkAsync();
        }

        private async UniTask FallAsync()
        {
            await UniTask.WaitForSeconds(_fallDelay);

            var axis = Quaternion.Euler(0, Random.value * 360, 0) * Vector3.forward;

            var initialRotation = transform.rotation;
            var finalRotation = initialRotation * Quaternion.AngleAxis(90, axis);

            var t = 0f;
            while (t < 1)
            {
                t += Time.deltaTime / _fallDuration;

                transform.rotation = Quaternion.Lerp(initialRotation, finalRotation, _fallRotationCurve.Evaluate(t));

                await UniTask.NextFrame();
            }

            transform.rotation = finalRotation;
        }

        private async UniTask SinkAsync()
        {
            await UniTask.WaitForSeconds(_sinkDelay);

            var initialY = transform.position.y;
            var finalY = initialY - _sinkDepth;

            while (transform.position.y > finalY)
            {
                transform.position += Vector3.down * _sinkSpeed * Time.deltaTime;

                await UniTask.NextFrame();
            }

            transform.position = new Vector3(transform.position.x, finalY, transform.position.z);
        }
    }
}