Disorient on the Murder Express
You'll likely want to download this wonderfully silly send-up of the detective game based on its name alone, but it manages to live up to that billing. It may not be the "first great detective game" – that game doesn't exist yet, sadly – but Disorient more than makes up for it by being legitimately funny. Knowledge of Agatha Christie's seminal detective novel certainly will make it even funnier, but it's far from necessary.
Play Disorient on the Murder Express at Itch.io