Sets the Orthographic Size of the main camera to make sure that the play area stays in view. The min vertical and horizontal units are relative to the center of the screen, the same as the Orthographic Size value.

ortho_aspect_fixer_dynamic_window_size.cs

class OrthoAspectFixer : MonoBehavior {
  private Camera _mainCamera;
  public int minVerticalUnits;
  public int minHorizontalUnits;
  
  void Start() {
    this._mainCamera = Camera.main;
  }

  void Update() {
    this._mainCamera.orthographicSize = Math.Max(this.minVerticalUnits, this.minHorizontalUnits / this._mainCamera.aspect);
  }
}

ortho_aspect_fixer_fixed_window_size.cs

class OrthoAspectFixer : MonoBehavior {
  public int minVerticalUnits;
  public int minHorizontalUnits;
  
  void Start() {
    var mainCamera = Camera.main;
    mainCamera.orthographicSize = Math.Max(this.minVerticalUnits, this.minHorizontalUnits / mainCamera.aspect);
  }
}