architectural block 3d model

Create a 3D model of a multi-room building block. The building should have a simple modular structure with walls, door openings, and window openings, but no interior details or furniture. All rooms must be completely empty inside. Use clean geometry, low to mid poly, game-ready topology. Floors, walls and ceilings should be separated correctly. Include several rooms connected by doorways, a simple corridor, and optionally a staircase shaft (without stairs). No textures needed or use simple neutral materials. The model should be optimized for game engines such as Roblox or Unity.