The rapid advancement of Large Language Models (LLMs) raises fundamental questions about the limits of AI in software development. This paper investigates whether a complete and playable multi-platform web-based game can be developed using only natural language prompts with an advanced LLM, Gemini 2.5 Pro. To explore this, the study compares two opposing development methodologies without the use of a traditional game engine. The study concludes that creating a playable game with prompts alone is possible, but only through a structured, iterative process. This positions the AI not as an autonomous developer, but as a powerful co-pilot that requires skilled, step-by-step guidance from a human expert.