Create a modern advertising poster for "UrbanFlex", a multifunctional backpack d

Create a modern advertising poster for "UrbanFlex", a multifunctional backpack designed for urban everyday life and travel. En el centro de la imagen, the backpack is prominently positioned, view from a slightly inclined angle, showing its front and side. The backpack has a sleek and contemporary design, with clean lines and a durable fabric finish, available in a matte black color with metallic gray accents. The poster background is a stylized cityscape, with tall buildings, Ruas movimentadas, and city lights at dusk. The background colors are soft, with shades of gray and dark blue, creating a contrast that makes the backpack stand out visually.