Q;  How would I write a basic screen saver (like, blank the screen) in Delphi?

A:  An easy implementation would be something like this:

var
  f: tForm;

begin
  f := tForm.create(self);
  f.WindowState := wsMaximized;
  f.color := black;
  f.borderStyle := bsNone;
  f.show;
end;

There is more to do, of course.  You must have a way back from there.  Perhaps an actual form that has a mouse click event programmed to f.close it.  Also, you want to hide the mouse.  Etc, etc.  But, this answers the question.