3D Model: A Rugged Utility-style Black Backpack Inspired By Carhartt Design. The Backpack Should Have A Durable Rectangular Shape With A Front Flap Secured By Two Vertical Buckle Straps And Mesh Side Pockets. Include A Small, Removable-looking Solar Panel Seamlessly Integrated On The Top Flap — Not Flashy Or Too Visible, Just A Functional Panel That Blends With The Design. Also Include A Visible USB Port On One Side, Neatly Embedded Without Exposed Cables. Use Matte Black Fabric For The Main Body, Matte Black Plastic For Buckles, And Slightly Glossy Black For The Solar Panel. No Logos. Maintain A Tough, Minimalist, And Practical Appearance