unfinished concrete building 3d model

A low-poly 3D game asset of a 4-story unfinished concrete building under construction. Architectural design features only raw gray concrete skeleton, load-bearing pillars, and structural slabs. NO walls, NO windows. Include functional, accessible concrete staircases between all floors. Stairs must have distinct, walkable geometry. Clean low-poly aesthetic, modular urban style consistent with city district assets. Gray concrete textures, sharp edges, efficient game-ready mesh, walkable structural layout.