Doc says "a stroked rectangle has a size of rectangle.size()
plus the pen width".

Like all classic games, gameplay is tied to the framerate.

Use a transparent pixmap instead, since Qt supports that now.

...and we have to tell Qt to paint the background.

Now we have to kill timers individually.

Nowadays everything is buffered and composed, so we have to request that
the widget should be repainted later.

QShortcut is more powerful and easier to use.

We do the right thing automatically these days

All constructors of QObject subclasses used to take the object name
as a parameter.

Back in the old days, Windows only allowed eight character file names.

Leading spaces are just so much easier to work with.