gather-and-defend/Assets/Scripts/LevelManager/LevelManagerScript.cs

using UnityEngine;
using GatherAndDefend.LevelEditor;
using System.Collections;
using UnityEngine.Tilemaps;
using System.Threading.Tasks;
using System;

public delegate Task PlacementAnimationHandler(Vector3 position, TileBase tile, Action tilePlacement);
public class LevelManagerScript : SingletonBehaviour<LevelManagerScript>
{
    private Action updateAction = null;
    public bool loadOnStart = false;
    public Level firstLevel;
    async void Start()
    {
        LevelManager.Instance.LevelLoaded += Instance_LevelLoaded;
        if (loadOnStart && firstLevel)
        {
            await LevelManager.Instance.LoadLevel(firstLevel, placementAnimation: PlacementAnimation);
        }
    }

    void OnDestroy()
    {
        updateAction = null;
    }

    void Update()
    {
        updateAction?.Invoke();
    }

    private void Instance_LevelLoaded(Level level)
    {
        updateAction = LevelManager.Instance.UpdateLevel;
    }

    public static async Task PlacementAnimation(Vector3 position, TileBase tile, System.Action putTileOnTilemap)
    {
        float speed = 0;
        float acceleration = -9.81f;
        var tilePlaceholder = new GameObject("tile");
        var rend = tilePlaceholder.AddComponent<SpriteRenderer>();
        rend.sortingOrder = 10;
        rend.sortingLayerName = "Unit";

        if (tile is LevelTile)
        {
            rend.sprite = (tile as LevelTile).Sprite;
        }
        else
        {
            rend.sprite = (tile as Tile).sprite;
        }

        tilePlaceholder.transform.position = position + Vector3.up * Camera.main.orthographicSize * 2;

        var delta = tilePlaceholder.transform.position - position;
        var direction = delta.normalized;
        var signY = delta.y / Mathf.Abs(delta.y);
        
        while (true)
        {
            if (!tilePlaceholder) break;

            speed += acceleration * Time.deltaTime;
            tilePlaceholder.transform.position += direction * Time.deltaTime * speed;
            var newDelta = tilePlaceholder.transform.position - position;
            var newSign = newDelta.y / Mathf.Abs(newDelta.y);

            if (newSign != signY) break;

            await Task.Yield();
        }

        putTileOnTilemap.Invoke();
        Destroy(tilePlaceholder);
    }
}