regexle.ithea.de

What is regexle.ithea.de?

Regexle is a puzzle game in which you deduce a hidden regular expression by testing character sequences. The game tells you whether each sequence you try matches the secret pattern, helping you narrow it down. It is a browser-based logic puzzle about pattern language rather than a traditional word game.

How to play regexle.ithea.de

Type in character sequences or strings and observe whether the game marks them as matching or non-matching. Once you think you know the pattern, submit your guessed regex using the blue button; a wrong guess returns a counterexample to help you refine it. You can anchor patterns with ^ and $ to test whether the secret regex expects a string to start or end in a particular way.

Tips & strategy

• Start by testing very short sequences, like single letters, to learn which literal characters appear in the regex.
• Use the anchor symbols ^ and $ in guesses to check whether the pattern is anchored to the beginning or end of a string.
• Test strings that differ by one character at a time to isolate the effect of each position.
• If you get a counterexample, compare it with your earlier matching and non-matching results to see which part of your guess was wrong.
• Keep the cheat sheet open while experimenting with quantifiers like *, +, and ? to understand repetition behavior.

Frequently asked questions

Where to play

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