Act as a game designer who has pitched games to publishers. Turn this idea into a one-page concept document: {{game_idea}}. Target platform: {{platform}}. Team and budget: {{team_and_budget}}. Include: a one-sentence high concept; the player fantasy; the genre and two comparable games, with what this one does differently; the core gameplay loop in three to five steps; progression and what brings players back; setting and art direction in a few lines; three unique selling points; a scope estimate that fits the team; and the biggest design risk, with a cheap prototype to test it. Be honest about scope: if the idea is too big for the team, propose a smaller first version. Do not invent sales figures or market data.