LockOutWindow.cs

namespace AutoLogout
{
  public partial class LockoutWindow : Form
  {
    private readonly Label instructions;

    public LockoutWindow(CountdownTimer parent) {
      Text = "Pause screen";
      Icon = new Icon("Resources/icon-light.ico");
      FormBorderStyle = FormBorderStyle.None;
      ShowInTaskbar = false;
      StartPosition = FormStartPosition.Manual;
      BackColor = Color.Black;
      
      AutoScaleMode = AutoScaleMode.Dpi;
      AutoScaleDimensions = new SizeF(96F, 96F);

      instructions = new Label {
        Text = "Timer paused. Click anywhere to show the timer.",
        AutoSize = true,
        ForeColor = Color.DimGray,
        TextAlign = ContentAlignment.MiddleCenter
      };
      instructions.Click += parent.ReassertTopMost;

      Controls.Add(instructions);

      Shown += OnShown;
      Click += parent.ReassertTopMost;
    }

    private void OnShown(object? sender, EventArgs? e){
      Location = new Point(0, 0);
      TopMost = false;
      TopMost = true;
      
      if(Screen.PrimaryScreen != null) {
        Width = Screen.PrimaryScreen.Bounds.Width;
        Height = Screen.PrimaryScreen.Bounds.Height;
      }

      instructions.Location = new Point(
        (Width - instructions.Width) / 2,
        (Height - instructions.Height) / 2
      );
    }

    protected override void OnFormClosing(FormClosingEventArgs e)
    {
      e.Cancel = true;  // Prevents window from closing
    }
  }
}