Before you start: test every pattern with examples that should match and examples that should fail.
Level 1: literals and wildcards
Match cat in different positions, then match cat, cot, and cut with one pattern. Explain why c.t works before moving on.
Level 2: character classes and quantifiers
Build patterns for two uppercase letters followed by two digits, repeated a characters, and words with an optional letter.
Level 3: anchors and validation
Require the whole string to match. Compare [A-Z]{2}\d{2} with ^[A-Z]{2}\d{2}$ using values that contain the pattern in the middle.
Level 4: real-world formats
Try dates, phones, simple emails, URLs, and log lines. For every task, invent at least three negative cases.
Level 5: refactor and explain
Once a pattern works, make it readable and explain every token. The shortest Regex is not always the most maintainable Regex.
Next step: test it for real
Use the Playground to experiment with the pattern, then practice in the game with feedback on false positives and false negatives.