Mushroom Grotto in Bloons TD 6 becomes a high-difficulty endurance challenge in Impoppable mode, where bloons are stronger, income is heavily restricted, and every decision must be carefully planned from the early game. The map’s darkness mechanic adds an extra layer of complexity, requiring efficient use of visibility to ensure proper tower coverage across all lanes. To succeed, you need a cost-efficient early defense, strong mid-game scaling, and high-impact late-game towers to handle dense MOAB waves and fortified bloons.