# 221B The Curious Casebook > A novel lateral thinking game—solve mysteries by chatting with an AI detective! Canonical page: [https://chrome-stats.com/d/com.dena.game221b](https://chrome-stats.com/d/com.dena.game221b) ## Overview - **ID:** `com.dena.game221b` - **Platform:** Android - **Type:** Android app - **Status:** Removed - **Publisher:** Bezel Lab - **Category:** GAME\_PUZZLE - **Downloads:** 749 - **Version:** 1.1.0 - **Last updated:** 2026-02-16 - **First published:** 2026-01-08 - **Publisher country:** JP - **Size:** 102 MB - **Data as of:** 2026-04-09 - **Store listing:** [Google Play Store](https://play.google.com/store/apps/details?id=com.dena.game221b) - **Website:** [https://dena-221b.web.app/](https://dena-221b.web.app/) - **Privacy policy:** [https://dena-221b.web.app/us/privacy/index.html](https://dena-221b.web.app/us/privacy/index.html) ## Description This case cannot be solved with common sense.
Welcome to "221B The Curious Casebook."
This is a novel, "lateral thinking" game where you uncover the hidden truth in perplexing situations presented as story fragments (puzzles). You will be solving these puzzles through dialogue with a detective powered by cutting-edge AI (Large Language Model). Engage in chat-style Q&A sessions with the detective to get to the heart of each case.
Game Features
◆ Test Your Deductive Skills with "Lateral Thinking" ◆
There are situations that seem strange and unnatural at first glance. What truth lies hidden beneath the surface?
In this game, "lateral thinking"—free, creative reasoning unconstrained by assumptions and preconceptions—is the key to solving mysteries.
Put your brain to work and try asking questions no one else would image.
◆ A New Interactive Mystery Experience with State-of-the-Art Artificial Intelligence ◆
Ask anything you want about the case freely through text or voice input.
The AI detective will respond to your questions with one of three simple answers: "Yes," "No," or "Irrelevant." Enjoy a completely new gaming experience by extracting information from limited clues to piece together deductions that lead to the truth. The detective's expressions also change dynamically based on your questions—his reactions might even serve as clues.
◆ Packed with Replay Value ◆
When you solve a case, your deductive performance is rated S, A, or B based on "the number of questions asked," "hints used," and more. Aim for the highest "Overall S" rating on every puzzle!
Additionally, some puzzles feature special rules such as "time limits," "question limits," or "no hints allowed." Can your deductive skills prove their true worth under pressure?
How to Play
Check the Puzzle: First, read the puzzle describing a perplexing situation and understand what the mystery is.
Question the Detective: Ask the detective about anything you're curious about or want to confirm. Each question you ask consumes your stamina.
Build Your Deduction: Use the AI detective's "Yes/No/Irrelevant" responses as hints to gradually unravel the truth.
Helpful Features
Hints: If you're truly stuck, use a "Hint." You'll receive an important clue leading to the truth. However, using hints consumes stamina and affects your score.
Give Up: If you really can't figure it out, you can "Give Up." This consumes stamina but lets you see the answer.
Recommended Audience

Lovers of mystery novels and detective dramas
Puzzle game, Werewolf, and escape room enthusiasts
Those who want to sharpen their logical thinking and creativity
Those who want to experience a completely new type of game
Those interested in interacting with AI

Notice
This app is a trial version of "221B The Curious Casebook."
Due to the nature of AI (Large Language Model) unintended inappropriate expressions or responses that directly hint at the answer may occasionally be generated. ## Permissions and access ### Permissions - `android.permission.ACCESS_ADSERVICES_AD_ID` - `android.permission.ACCESS_ADSERVICES_ATTRIBUTION` - `android.permission.ACCESS_ADSERVICES_TOPICS` - `android.permission.ACCESS_NETWORK_STATE` - `android.permission.ACCESS_WIFI_STATE` - `android.permission.FOREGROUND_SERVICE` - `android.permission.INTERNET` - `android.permission.POST_NOTIFICATIONS` - `android.permission.VIBRATE` - `android.permission.WAKE_LOCK` - `com.android.vending.CHECK_LICENSE` - `com.applovin.array.apphub.permission.BIND_APPHUB_SERVICE` - `com.dena.game221b.DYNAMIC_RECEIVER_NOT_EXPORTED_PERMISSION` - `com.google.android.finsky.permission.BIND_GET_INSTALL_REFERRER_SERVICE` - `com.google.android.gms.permission.AD_ID` ## Similar extensions and apps - [221B -探偵の奇妙な推理録- (体験版)](https://chrome-stats.com/d/com.dena.ttob) — 2,844 users - [Ask and Solve: Mysteries](https://chrome-stats.com/d/com.askandsolve.mysteries) — 7 users - [Detective AI: Mystery Game](https://chrome-stats.com/d/com.star.detectiveai) — 18,721 users - [Dedektif AI: Case Files](https://chrome-stats.com/d/com.islamkocgurbuz.dedektifai) — 116 users - [Mystery AI Detective : Chat AI](https://chrome-stats.com/d/com.pione.situationpuzzles) — 10,725 users - [Detective Stories](https://chrome-stats.com/d/com.hurata.dedective_stories) — 54 users - [Detective AI: Yes No Mystery](https://chrome-stats.com/d/com.devbeing.detective) — 304 users - [Detectives Notebook](https://chrome-stats.com/d/com.detectivenotebook) — 124 users - [The Casebook: Detective Puzzle](https://chrome-stats.com/d/com.electronstudios.casebook) — 287 users - [Mentalist Detective](https://chrome-stats.com/d/com.nivagames.mentalistdetective) — 3,018 users - [AI Suspects: Unmask AI Crime](https://chrome-stats.com/d/com.versetech.aisuspect) — 1,434 users, 3.56 / 5 - [Open Verdict](https://chrome-stats.com/d/com.digitalhorizonsoftware.openverdict) — 213 users --- Source: [Chrome-Stats](https://chrome-stats.com/d/com.dena.game221b)