Writing Mystery Games in Vanilla JS: Interrogation Systems, Trust Trackers, and 6-Ending Medical Thrillers An indie developer built two narrative mystery games, Echo Chamber — An Interrogation Mystery and Flatline — A Medical Thriller, in vanilla JavaScript with no game engine or dependencies, each under 20 KB. The games use a state machine tracking suspicion/evidence or trust/doubt to drive branching dialogue and multiple endings, with features like typewriter text, Web Audio heartbeat synthesis, and SVG EKG animation. AI Disclosure: This article was written with AI assistance. All games mentioned were built using AI-assisted development tools. When indie devs think "browser game," they think platformers, idle clickers, or puzzles. But look at the itch.io HTML5 top charts: narrative-driven mystery and horror games dominate. FORGOTTEN. Exorcist Candy. Short, story-heavy experiences that load in a second and stay with you for hours. The technical question is: how do you build a narrative game without a game engine? No Unity. No Unreal. No Twine. Just an HTML file, a