You can, in fact, enter codes in the private game lobby. There are no in-game doors or pads to enter codes into, however.

Another classic in the line of games that allow numpad codes. Both the original classic versions and the Enhanced Edition allow you to enter codes with the numpad.

One of the progenitor games where you can enter codes with the numpad. Definitely on the list.

Lots of code entries, none of them can entered with the numpad.

You can use the numpad at all code entries.