Hey, here are some ideas I don't do (I keep one idea for me, if I found time to do it),
feel free to take or comment it, I write this post because I think it could be fun little games and I am sad to not doing it.
idea 1: the Borges way.
Inspired by An Examination of the Work of Herbert Quain. A basic dialog game. A kinda bad game: not challenging and really linear.
But one sentence at the end, reveals to you, that the detective you was playing was wrong. And if you get it, and you think about it, you can found the real solution....
(in he Borges' short, the sentence is: "Everybody were thinking that the meeting between the two chess players was fortuitous" (my bad translation of the french translation I had)
idea 2: the Papers, Please way.
(and Last express way too). You are a papers detective. You never move to your chair, just read reports. The screen is your desk.
You have two detective who works for you, at the start of your day, you can give your orders (interrogate, follow, confront suspects, or examine some place, etc.) (give orders via phone?) , then you read the reports of the last day.
When you think you have the solution, you prepare the folder for the judge: you can only put a limited number of reports (4? 5?) in the folder. Then you will just be informed of the judge's decision (classified case, arrest but acquittal, etc.)
idea 3: the logical way.
more simple game. you have a map of the place of a murder (with a corpse in a room), and suspects to put on the map for three different moments (before the murder, during the murder and after).
Each suspects have one affirmation for each moment ("I heard something at the room", "I was in the kitchen", "I move on", "I was with one person", etc.).
The goal is to place each suspect at the right place: the combination where all the affirmations are right, except those of the murderer (who can lie or not). And so found the murderer.
This fit well for a procedural game (but the hard part is to generate problem with a unique solution).
That's all. If someone do one of this games, I will be very proud. If not, I'm already happy that this ideas are somewhere and not just forgotten (this is a sort of memo post too)...
(and sorry for the big post in bad English)