Kisimoko developed a pen thickness customization feature for the semicolon213/2024_GuestBook_T1 drawing tool, focusing on enhancing user control and editing precision. Using C++ and the Windows API, Kisimoko designed and implemented new GUI elements that allow users to adjust and visualize pen thickness in real time. The solution integrated seamlessly with the existing color selection interface, maintaining a cohesive and intuitive user experience. This work addressed the need for more granular drawing options, aligning with the product’s roadmap for improved editing capabilities. The feature was delivered with attention to UI consistency and technical integration, demonstrating solid GUI development skills.