add grid building system

Assets/Scripts/GridBuildingSystem.cs

@@ -0,0 +1,61 @@
+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+using UnityEngine.Tilemaps;
+
+public class GridBuildingSystem : MonoBehaviour
+{
+  public PlaceableObject placeableObject;
+
+
+  public Tilemap collisionTm;
+
+  GameObject newBuilding;
+
+
+  private void Start()
+  {
+    newBuilding = Instantiate(placeableObject.prefab, Vector3.zero, Quaternion.identity);
+  }
+  private void Update()
+  {
+    if (newBuilding)
+    {
+      Vector3 newPosition = Camera.main.ScreenToWorldPoint(Input.mousePosition);
+      //* Cursor.visible = false;
+      int snappedX = Mathf.RoundToInt(newPosition.x);
+      int snappedY = Mathf.RoundToInt(newPosition.y);
+      Vector3Int snappedPosition = new Vector3Int(snappedX, snappedY, 0);
+
+      newBuilding.transform.position = snappedPosition;
+
+      // TODO change to red if occupied
+
+      if (Input.GetMouseButtonDown(0) && !IsOccupied(snappedPosition, placeableObject))
+      {
+        placeableObject.Place();
+        // TODO mark tiles as occupied
+        // TODO unselect
+      }
+    }
+
+  }
+
+  private bool IsOccupied(Vector3Int startPos, PlaceableObject po)
+  {
+    Vector3Int poSize = new Vector3Int(po.width, po.height, 1);
+
+    BoundsInt area = new BoundsInt(startPos, poSize);
+    TileBase[] tileArray = collisionTm.GetTilesBlock(area);
+
+    foreach (TileBase tile in tileArray)
+    {
+      if (tile != null)
+      {
+        return true;
+      }
+    }
+
+    return false;
+  }
+}