The "you've been to Afghanistan, I perceive" scene lives rent-free in my head. So I made a daily game out of it.
My favorite thing in the whole BBC run is the first lab scene. Sherlock looks at John for ten seconds and says "Afghanistan or Iraq?" The reasoning chain (tan line stops at the wrist, military bearing, healing limp, brother's phone) is the most addictive piece of writing in the show for me.
So I built a daily game around it. Every day there's a new photograph of a person. You write down what you observe and the deductions you can pull from it. An AI scores your reasoning and tells you what you missed. Some days I'm proud of myself, some days it points at something obvious in the background and I feel like Lestrade.
It's at dailyholmes.com Free, no signup, runs in the browser. Takes about three minutes a day.
This community knows what good deduction sounds like better than anyone. If you try it, I'd really love to hear when the AI scores something wrong or misses a deduction that was clearly there. That feedback is what's going to make the game actually good.