AngelSanchezT/21-days-python-challenge ? reverse-engineered prompt

Build me a clean 21 day Python learning challenge project for beginners.

I want each day to have a short explanation, a practical exercise, and a simple solution file, so someone can learn Python step by step without feeling lost. The first few days should cover basic things like checking types, calculating a tip, figuring out if a year is a leap year, and using loops to draw a triangle. Keep the exercises easy to follow, and make sure the code is clear and beginner friendly.

Please also include tests for the exercises with pytest, and make the README easy to understand for someone starting from scratch. If it helps, include both English and Spanish instructions like a learning repo would. Keep the structure organized so it feels like a real 21 day challenge people can run through one day at a time. If you need to look up current docs online, go ahead.