Looking at the README for Red Alert specifically and the various requirements, how is it possible that these run on modern Windows? OFC they're distributed via

Looking at the README for Red Alert specifically and the various requirements, how is it possible that these run on modern Windows? OFC they're distributed via Steam as binaries + libs etc, but are they including these ancient versions of DirectX and the other dependencies with the downloads? Are these still compatible? I know Windows has/had for years remarkable backwards compatibility, but that's always been a source of confusion for me. Is there some monstrous "compatibility shim" somewhere for old DirectX APIs or something? What makes this possible? Edit: Wait was this a re-release at some point more recently? If so, I suppose that specific question is addressed, but that still pertains to other old games. How does Half-Life (or whatever) still work? Same story?