Miniature

When a game become a mniature, under 20, 30 moves ?  

I think it's 25, not sure though...

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Miniature

A short game (usually no more than 20 to 25 moves), for example 1.e3 e5 2.Qf3 d5 3.Nc3 e4 4.Qf4?? Bd6! and White resigned in NN-Künzel because his queen is trapped. However, a significant minority of authors include games up to 30 moves. John Nunn, 101 Brilliant Chess Miniatures, Gambit Publications, 1999, p. 6. ISBN 1-901983-16-1. Usually only decisive games (not draws) are considered miniatures. Ideally, a miniature should not be spoiled by an obvious blunder by the losing side. A miniature may also qualify as a brilliancy. The Opera game is a famous example. Sometimes called a brevity (chiefly British).

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source: http://en.wikipedia.org/wiki/Glossary_of_chess#Miniature

Thanks to the great wiki.

Here's one, written by David Ellis, chess editor of the 'The West Australian'

Vasilios Kostronias vs Xiu Deshun
2011 Aeroflot Open, Rd 6  Sicilian Najdorf