low-poly house interior 3d model

Create a complete, enclosed, watertight low-poly flat-shaded 2-story house interior for a multiplayer party game. Style: solid flat colors, NO textures, NO normal maps, roughness 0.9+, simple diffuse materials only, clean faceted geometry. CRITICAL: all walls must be SOLID double-sided geometry with 0.2m thickness, NOT thin single-sided planes. Include a FULL CEILING on every room — no open tops, no dollhouse cutaway. Every room must be a fully enclosed box with 4 walls + floor + ceiling. NO gaps, NO holes, NO floating artifacts, NO disconnected geometry. All walls must connect properly to adjacent walls and to floor/ceiling. Ground floor (30m×16m, 3.2m ceiling height): living room 10×8m with central table, kitchen 6×5m with island, hallway 4×10m, bedroom 6×5m, bathroom 3×3m, staircase 3×5m. Second floor (24m×12m, 2.8m ceiling): hallway 4×8m, bedroom1 6×5m, bedroom2 5×4m, bathroom 3×3m, attic 5×6m with sloped ceiling 2.4–3m. Door openings cut into walls: 2m wide × 2.5m tall. 18-step st