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ExplainerYahoo closes GeoCities: how the web lost millions of home pagesYahoo bought GeoCities for billions in 1999 and switched it off a decade later. The closure became a turning point for web preservation.ExplainerThe Storm worm: the botnet that started with a weather headlineIn January 2007 an email about deadly storms in Europe spread a Trojan that built one of the largest peer-to-peer botnets of its time.ExplainerGPLv3: how the free software licence was rewrittenAfter 18 months of public drafting, the Free Software Foundation published version 3 of the GNU General Public License in June 2007.ExplainerThe UK identity card scheme: from Act of Parliament to shredded registerBritain legislated for national ID cards backed by a central biometric register, then abolished the whole scheme within five years.ExplainerThe netbook era: small, cheap laptops that briefly drove PC growthThe Asus Eee PC started a boom in low-cost mini laptops that propped up PC sales, until tablets and thinner laptops took their place.

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Sudoku

Fill the grid so every row, column and 3×3 box contains the digits 1 to 9 exactly once. Each puzzle is generated in your browser and has a single solution.

Generating…

How to play

Click a square and type a digit from 1 to 9. Use Check to highlight squares that conflict with the solution, Hint to reveal one square, or Solve to show the full answer.

Tips

Start with rows, columns or boxes that already have the most digits. Look for the only square in a box where a digit can go, then repeat. Harder puzzles need you to track candidates: write down which digits are still possible in each square and eliminate them as you go.