Curly's Law
A principle of software design and life: focus on doing one thing well. Derived from the movie City Slickers, it argues that clarity comes from singular focus.
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Origin
Named after Curly in the 1991 film City Slickers, played by Jack Palance, who holds up one finger and says the secret to life is “one thing.” In software engineering, the principle was popularized by Jeff Atwood (Coding Horror, Stack Overflow), who connected it to the Unix philosophy of writing programs that do one thing well.
Updated February 22, 2026