Why Undertale Bet on GameMaker Studio and GML: The Beginner Engine Behind a 5-Million-Copy Morality RPG

Why solo dev Toby Fox built 5M-copy Undertale in niche GameMaker Studio + GML instead of Unity, what the 2D object/event model gained and cost, and what indie devs can steal about battle-first prototyping and port strategy — with original analysis and open questions.