Pencil Project is an open-source GUI prototyping tool that is ideal for creating mock-ups of user interfaces for both mobile and web applications. Its intuitive interface and rich set of features allow designers, developers, and product managers to easily draft layouts and share mock-up designs. The tool offers a variety of built-in shapes, as well as support for adding external objects, which makes it incredibly versatile for designing detailed and accurate representations of user interfaces. Pencil Project supports multiple export formats, including PNG, HTML, and PDF, enabling easy sharing and presentation. The project's website is located at http://pencil.evolus.vn/, where users can download the tool, find additional resources, and access community support.