Write a typography system definition in a {{tone}} tone for {{brand_name}}, a neobanking brand targeting {{target_audience}}. The system must embody a {{visual_style}} aesthetic. Be practical and actionable for designers and developers. Use Markdown headings. Cover: Design Principles, Font Selection, Type Hierarchy, Spacing and Rhythm, and Usage Guidelines. Maximum 500 words. Paste any relevant background information after these instructions before running.