FerreiraArth/JS ? reverse-engineered prompt

Build me a simple JavaScript practice project that includes a basic task manager in Portuguese, with a way to add, mark, and remove tasks, plus a few small DOM examples and some folders for past tests and set based exercises. I want it to feel like a beginner friendly codebase that I can open and understand quickly, with clear separation between the different practice areas. Keep the interface clean and simple, and make the task part the main focus so it actually feels useful, not just like a demo.

If you need to, look up current docs online for any browser or JavaScript details. Make sure the code is easy to run and easy to extend later, and organize things so I can keep adding new exercises or test solutions without everything getting messy.