A lot of those were written in assembly by teenagers, using WinAPI directly. Yet they still run on Win10/Win11. A lost art.
It wasn’t all assembly (though those were the popular ones), heavy C use too. What really changed the game was when DirectX came.
Do you know where I can find source code for such intros?
Thematically, many of them resemble the kind of WordArt we used to make as children in MS Word.
Win32 is definitely not a lost art. It's more accessible than ever with modern code generation tools like cswin32.
This inspiration to build things that look like this is what has been lost.