Create a low-poly, stylized 3D model of military army barracks for a Unity game. The barracks should be a long rectangular structure with a green or camo-colored exterior, metal roof, and small windows along the sides. Add a few exterior details like a wooden door, steps, vents, and sandbags around the base. The model should be game-ready, optimized for real-time use, with no interior and a clean UV map for easy texturing. Keep poly count low to medium for mobile or indie game performance."