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README.md

@@ -26,7 +26,9 @@ For each notebook you can hover on the title to see a description, or click the
 
 |Run|Year|New|
 |---|---|---|
-| [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/TruncatablePrimes.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FTruncatablePrimes.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FTruncatablePrimes.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/TruncatablePrimes.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/TruncatablePrimes.ipynb) | <u>2026</u> | <a href="ipynb/TruncatablePrimes.ipynb" title="Prime numbers where you can remove digits and still get primes.">Truncatable Primes</a> |
+| [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/clvr.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2Fclvr.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2Fclvr.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/clvr.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/clvr.ipynb) | 2026 | <a href="ipynb/clvr.ipynb" title="Guess famous phrases from letter shapes. Beginner level.">Did you solve it? R y clvr ngh t rd ths sntnc?</a> |
+| [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/Euler3.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FEuler3.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FEuler3.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/Euler3.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/Euler3.ipynb) | 2026 | <a href="ipynb/Euler3.ipynb" title="Find the largest prime factor of a number">Project Euler #3: Largest prime factor</a> |
+| [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/TruncatablePrimes.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FTruncatablePrimes.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FTruncatablePrimes.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/TruncatablePrimes.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/TruncatablePrimes.ipynb) | 2026 | <a href="ipynb/TruncatablePrimes.ipynb" title="Prime numbers where you can remove digits and still get primes.">Truncatable Primes</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/Advent-2025.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FAdvent-2025.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FAdvent-2025.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/Advent-2025.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/Advent-2025.ipynb) | 2025 | <a href="ipynb/Advent-2025.ipynb" title="Puzzle site with a coding puzzle for 12 days of Christmas, December 2025">Advent of Code 2025</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/Advent-2025-AI.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FAdvent-2025-AI.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FAdvent-2025-AI.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/Advent-2025-AI.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/Advent-2025-AI.ipynb) | 2025 | <a href="ipynb/Advent-2025-AI.ipynb" title="Using large language coding models to solve AoC puzzles">Advent of Code 2025: AI LLM Edition</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/Advent-2024.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FAdvent-2024.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FAdvent-2024.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/Advent-2024.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/Advent-2024.ipynb) | 2024 | <a href="ipynb/Advent-2024.ipynb" title="Puzzle site with a coding puzzle each day of Advent, December 2024">Advent of Code 2024</a> |
@@ -97,13 +99,14 @@ For each notebook you can hover on the title to see a description, or click the
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/How%20To%20Count%20Things.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FHow%20To%20Count%20Things.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FHow%20To%20Count%20Things.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/How%20To%20Count%20Things.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/How%20To%20Count%20Things.ipynb) | 2020 | <a href="ipynb/How%20To%20Count%20Things.ipynb" title="Combinatorial math: how to count how many things there are, when there are a lot of them">How to Count Things</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/KenKen.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FKenKen.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FKenKen.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/KenKen.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/KenKen.ipynb) | 2021 | <a href="ipynb/KenKen.ipynb" title="A Sudoku-like puzzle, but with arithmetic.">KenKen (Sudoku-like Puzzle)</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/NumberBracelets.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FNumberBracelets.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FNumberBracelets.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/NumberBracelets.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/NumberBracelets.ipynb) | 2024 | <a href="ipynb/NumberBracelets.ipynb" title="A game involving numbered beads on a circular bracelet.">Number Bracelets Game</a> |
+| [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/Euler3.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FEuler3.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FEuler3.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/Euler3.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/Euler3.ipynb) | 2026 | <a href="ipynb/Euler3.ipynb" title="Find the largest prime factor of a number">Project Euler #3: Largest prime factor</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/Socks.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FSocks.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FSocks.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/Socks.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/Socks.ipynb) | 2019 | <a href="ipynb/Socks.ipynb" title="What is the probability that you will be able to pair up socks as you randomly pull them out of the dryer?">Pairing Socks</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/Sicherman%20Dice.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FSicherman%20Dice.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FSicherman%20Dice.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/Sicherman%20Dice.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/Sicherman%20Dice.ipynb) | 2018 | <a href="ipynb/Sicherman%20Dice.ipynb" title="Find a pair of dice that is like a regular pair of dice, only different">Sicherman Dice</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/Golomb-Puzzle.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FGolomb-Puzzle.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FGolomb-Puzzle.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/Golomb-Puzzle.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/Golomb-Puzzle.ipynb) | 2014 | <a href="ipynb/Golomb-Puzzle.ipynb" title="A Puzzle involving placing rectangles of different sizes inside a square">Sol Golomb's Rectangle Puzzle</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/Stubborn.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FStubborn.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FStubborn.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/Stubborn.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/Stubborn.ipynb) | 2024 | <a href="ipynb/Stubborn.ipynb" title="Any number ending in 5 has a square that also ends in 5. What other endings are like this?">Stubborn number endings</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/StarBattle.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FStarBattle.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FStarBattle.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/StarBattle.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/StarBattle.ipynb) | 2021 | <a href="ipynb/StarBattle.ipynb" title="Fill-in-the-grid puzzle similar to Sudoku">Star Battle (Sudoku-like Puzzle)</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/Sudoku.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FSudoku.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FSudoku.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/Sudoku.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/Sudoku.ipynb) | 2006 | <a href="ipynb/Sudoku.ipynb" title="Classic fill-in-the-grid puzzle">Sudoku</a> |
-| [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/SudokuJava.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FSudokuJava.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FSudokuJava.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/SudokuJava.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/SudokuJava.ipynb) | 2021 | <a href="ipynb/SudokuJava.ipynb" title="A version of the Sudoku solver using parallel threads and other optimizations">Sudoku: 100,000 puzzles/second in Java</a> |
+| [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/SudokuJava.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FSudokuJava.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FSudokuJava.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/SudokuJava.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/SudokuJava.ipynb) | 2021 | <a href="ipynb/SudokuJava.ipynb" title="A version of the Sudoku solver using parallel threads and other optimizations">Sudoku: 200,000 puzzles/second in Java</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/SquareSum.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FSquareSum.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FSquareSum.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/SquareSum.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/SquareSum.ipynb) | 2020 | <a href="ipynb/SquareSum.ipynb" title="Place the numbers from 1 to n in a chain (or a circle) such that adjacent pairs sum to a perfect square">Square Sum Puzzle</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/Cheryl.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FCheryl.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FCheryl.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/Cheryl.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/Cheryl.ipynb) | 2020 | <a href="ipynb/Cheryl.ipynb" title="Solving the *Cheryl's Birthday* logic puzzle">When is Cheryl's Birthday?</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/Cheryl-and-Eve.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FCheryl-and-Eve.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FCheryl-and-Eve.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/Cheryl-and-Eve.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/Cheryl-and-Eve.ipynb) | 2015 | <a href="ipynb/Cheryl-and-Eve.ipynb" title="Inventing new puzzles in the Style of Cheryl's Birthday">When Cheryl Met Eve: A Birthday Story</a> |
@@ -116,6 +119,7 @@ For each notebook you can hover on the title to see a description, or click the
 |---|---|---|
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/Boggle.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FBoggle.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FBoggle.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/Boggle.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/Boggle.ipynb) | 2020 | <a href="ipynb/Boggle.ipynb" title="Find all the words on a Boggle board; then find a board with a lot of words">Boggle / Inverse Boggle</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/ElementSpelling.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FElementSpelling.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FElementSpelling.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/ElementSpelling.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/ElementSpelling.ipynb) | 2020 | <a href="ipynb/ElementSpelling.ipynb" title="Spelling words using the chemical element symbols, like CoIn">Chemical Element Spelling</a> |
+| [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/clvr.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2Fclvr.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2Fclvr.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/clvr.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/clvr.ipynb) | 2026 | <a href="ipynb/clvr.ipynb" title="Guess famous phrases from letter shapes. Beginner level.">Did you solve it? R y clvr ngh t rd ths sntnc?</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/equilength-numbers.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2Fequilength-numbers.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2Fequilength-numbers.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/equilength-numbers.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/equilength-numbers.ipynb) | 2020 | <a href="ipynb/equilength-numbers.ipynb" title="What number names have the same letter count as the number they name (such as FOUR)?">Equilength Numbers: FOUR = 4</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/Gesture%20Typing.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FGesture%20Typing.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FGesture%20Typing.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/Gesture%20Typing.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/Gesture%20Typing.ipynb) | 2017 | <a href="ipynb/Gesture%20Typing.ipynb" title="What word has the longest path on a gesture-typing smartphone keyboard?">Gesture Typing</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/Ghost.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FGhost.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FGhost.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/Ghost.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/Ghost.ipynb) | 2017 | <a href="ipynb/Ghost.ipynb" title="The word game Ghost (add letters, try to avoid making a word)">Ghost: A Word game</a> |
@@ -159,7 +163,7 @@ For each notebook you can hover on the title to see a description, or click the
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/Differentiation.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FDifferentiation.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FDifferentiation.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/Differentiation.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/Differentiation.ipynb) | 2017 | <a href="ipynb/Differentiation.ipynb" title="A computer algebra system, including symbolic differentiation">Symbolic Algebra, Simplification, and Differentiation</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/Snobol.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FSnobol.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FSnobol.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/Snobol.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/Snobol.ipynb) | 2017 | <a href="ipynb/Snobol.ipynb" title="As a student, did you ever get a bad grade on a programming assignment?">Snobol: Bad Grade, Good Experience</a> |
 | [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/TSP.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FTSP.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FTSP.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/TSP.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/TSP.ipynb) | 2018 | <a href="ipynb/TSP.ipynb" title="Another of the classics">Traveling Salesperson Problem</a> |
-| [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/TruncatablePrimes.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FTruncatablePrimes.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FTruncatablePrimes.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/TruncatablePrimes.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/TruncatablePrimes.ipynb) | <u>2026</u> | <a href="ipynb/TruncatablePrimes.ipynb" title="Prime numbers where you can remove digits and still get primes.">Truncatable Primes</a> |
+| [C](https://colab.research.google.com/github/norvig/pytudes/blob/main/ipynb/TruncatablePrimes.ipynb) [D](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmain%2Fipynb%2FTruncatablePrimes.ipynb) [M](https://mybinder.org/v2/gh/norvig/pytudes/main?filepath=ipynb%2FTruncatablePrimes.ipynb) [N](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/main/ipynb/TruncatablePrimes.ipynb) [S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes/blob/main/ipynb/TruncatablePrimes.ipynb) | 2026 | <a href="ipynb/TruncatablePrimes.ipynb" title="Prime numbers where you can remove digits and still get primes.">Truncatable Primes</a> |
 
 # Index of Python Files
 

ipynb/clvr.ipynb

@@ -0,0 +1,715 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "id": "9e54c615-5dab-4642-924f-f2840558ff9e",
+   "metadata": {},
+   "source": [
+    "<div align=\"right\" style=\"text-align: right\"><i>Peter Norvig<br>April 2026</i></div>\n",
+    "\n",
+    "# Did you solve it? R y clvr ngh t rd ths sntnc?\n",
+    "\n",
+    "Alex Bellos's [30 March 2026 column](https://www.theguardian.com/science/2026/mar/30/did-you-solve-it-r-y-clvr-ngh-t-rd-ths-sntnc) asks us to guess famous phrases or sayings, given the shapes of the rectangles that bound the letters, and the clue that vowels are <span style=\"color:green\">**green**</span> and consonants are <span style=\"color:blue\">**blue**</span>.  \n",
+    "\n",
+    "Here's one of the puzzles:\n",
+    "\n",
+    "![](https://i.guim.co.uk/img/media/dd62fe8dfdc6eb9d98815a2e14791ae268aa4d46/0_0_580_75/master/580.jpg?width=310&dpr=2&s=none&crop=none)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "6a2c1014-5894-4bf0-b4b3-5f1d1561fa2a",
+   "metadata": {},
+   "source": [
+    "I can help solve this problem by using code to constrain what each letter and each word might be.\n",
+    "\n",
+    "I'll start by defining different subsets of letters: `v` for the vowels, `c` for the consonants, `a` for the letters whose shape ascends above the norm, etc.:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 24,
+   "id": "628d38c1-0671-49dd-9897-7bd5eff196ee",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "letters = set('abcdefghijklmnopqrstuvwxyz')\n",
+    "v = set('aeiou')    # vowels (green)\n",
+    "c = letters - v     # consonants (blue)\n",
+    "\n",
+    "a = set('bdfhijlt') # ascending\n",
+    "d = set('gjpqy')    # descending\n",
+    "b = letters - a - d # block: neither ascending nor descending\n",
+    "\n",
+    "t = set('li')       # thin\n",
+    "w = set('mw')       # wide\n",
+    "n = letters - t - w # normal: neither wide nor thin"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "f51d68da-7569-4bdd-97a2-3c245e143c70",
+   "metadata": {},
+   "source": [
+    "Now I can say that the first letter of the first word above (the green rectangle) is a block-shaped vowel; the intersection of the **b**lock and **v**owel sets, denoted in Python with the `&` operator:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "id": "1f17f9ce-0e88-464d-80e6-53a458b3594b",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "{'a', 'e', 'o', 'u'}"
+      ]
+     },
+     "execution_count": 2,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "b&v"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "de4886ea-0244-4582-8a43-9fae9daceb9a",
+   "metadata": {},
+   "source": [
+    "The first word has three letters, `b&v` followed by two **a**scending **t**hin **c**onsonants, `a&t&c`:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "id": "df3a9acf-e4df-42eb-8eb0-61fbdda7b598",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "[{'a', 'e', 'o', 'u'}, {'l'}, {'l'}]"
+      ]
+     },
+     "execution_count": 3,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "[b&v, a&t&c, a&t&c]"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "b3945fa3-587c-4155-b201-ed7aa55510e5",
+   "metadata": {},
+   "source": [
+    "Neat! There is only one **a**scending **t**hin **c**onsonant, `'l'`.\n",
+    "\n",
+    "The whole puzzle is as follows (I made the apostrophe be a word of its own):"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "id": "b4b5bb61-08f6-4815-9f46-ff1dd8e5816c",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "[[{'a', 'e', 'o', 'u'}, {'l'}, {'l'}],\n",
+       " [{'b', 'd', 'f', 'h', 'j', 'l', 't'},\n",
+       "  {'b', 'd', 'f', 'h', 'j', 'l', 't'},\n",
+       "  {'a', 'e', 'o', 'u'}],\n",
+       " [{'m', 'w'},\n",
+       "  {'a', 'e', 'o', 'u'},\n",
+       "  {'c', 'k', 'm', 'n', 'r', 's', 'v', 'w', 'x', 'z'},\n",
+       "  {'b', 'd', 'f', 'h', 'j', 'l', 't'},\n",
+       "  {'b', 'd', 'f', 'h', 'j', 'l', 't'}],\n",
+       " [{'’'}],\n",
+       " [{'c', 'k', 'm', 'n', 'r', 's', 'v', 'w', 'x', 'z'}],\n",
+       " [{'a', 'e', 'o', 'u'}],\n",
+       " [{'c', 'k', 'm', 'n', 'r', 's', 'v', 'w', 'x', 'z'},\n",
+       "  {'b', 'd', 'f', 'h', 'j', 'l', 't'},\n",
+       "  {'a', 'e', 'o', 'u'},\n",
+       "  {'g', 'j', 'p', 'q', 'y'},\n",
+       "  {'a', 'e', 'o', 'u'}]]"
+      ]
+     },
+     "execution_count": 4,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "puzzle3 = [[b&v, a&t&c, a&t&c], [a&c, a&c, b&v], [w&c, b&v, b&c, a&c, a&c], [{\"’\"}], [b&c], [b&v], [b&c, a&c, b&v, d&c, b&v]]\n",
+    "puzzle3"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "50586a9e-2a63-4c43-858e-509e783aa99f",
+   "metadata": {},
+   "source": [
+    "## Possible Words\n",
+    "\n",
+    "What combinations of letters can each word pattern make? The function `possible_words` goes through the pattern one letter set at a time and builds up all possible ways of adding each possible letter to each possible partial word string:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 5,
+   "id": "664292e4-416c-4408-bc9a-a5df0f2ede08",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "def possible_words(pattern: list[set[str]]) -> set[str]:\n",
+    "    \"\"\"All ways of choosing one letter from each of the possible letters in the word pattern.\"\"\"\n",
+    "    words = {''} # To start there is one possible partial word, with no letters\n",
+    "    for letter_set in pattern:\n",
+    "        # On each turn, add each possible letter to each possible partial word\n",
+    "        words = {word + letter for word in words for letter in letter_set}\n",
+    "    return words"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "c3de036e-7ca3-45f5-99ca-ead670ced8a0",
+   "metadata": {},
+   "source": [
+    "For example,"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 6,
+   "id": "2743ba3a-0474-4f04-91cf-7ea57550b74c",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "{'all', 'ell', 'oll', 'ull'}"
+      ]
+     },
+     "execution_count": 6,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "possible_words([b&v, a&t&c, a&t&c])"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "d213da56-3d0b-4344-ab09-6a676b11a1f2",
+   "metadata": {},
+   "source": [
+    "Another example:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 7,
+   "id": "0a8cb3da-3d3d-4241-9d22-8b50c16aeb8d",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "{'ban', 'bat', 'bon', 'bot', 'can', 'cat', 'con', 'cot'}"
+      ]
+     },
+     "execution_count": 7,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "possible_words([{'b', 'c'}, {'a', 'o'}, {'n', 't'}])"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "799abea2-83a4-4d71-bd04-270ff056249a",
+   "metadata": {},
+   "source": [
+    "Let's trace through how `possible_words` works on this example. It starts with one possible partial word, the empty string:\n",
+    "\n",
+    "    words = {''}\n",
+    "\n",
+    "Then it enterts the `for` loop and looks at the first letter set, `{'b', 'c'}`, and adds each letter to each partial word (just one of them: the empty string) to get a set of two partial words:\n",
+    "\n",
+    "    words = {'b', 'c'}\n",
+    "\n",
+    "It does the same thing with the second letter set, `{'a', 'o'}`, to get a set of four partial words:\n",
+    "\n",
+    "    words = {'ba', 'bo', 'ca', 'co'}\n",
+    "\n",
+    "Finally, it considers the third letter set, `{'n', 't'}`, and gets the final answer, a set of eight words:\n",
+    "\n",
+    "    words = {'ban', 'bat', 'bon', 'bot', 'can', 'cat', 'con', 'cot'}\n",
+    "\n",
+    "## Dictionary Words\n",
+    "\n",
+    "What actual dictionary words could a pattern stand for? To answer that I'll need a list of actual dictionary words. Furthermore, when `possible_words(pattern)` returns more than one word, I'll have to pick one. To facilitate that, I will use a word list that includes the frequency of each word so that I can pick the word with the highest frequency. \n",
+    "\n",
+    "I'll download the word list file \"[count_big.txt](count_big.txt)\" which has the format: \n",
+    "\n",
+    "    a           21160\n",
+    "    aah         1\n",
+    "    aaron       5\n",
+    "    ab          2\n",
+    "    aback       3\n",
+    "    abacus      1\n",
+    "    abandon     32\n",
+    "    abandoned   72\n",
+    "    abandoning  27\n",
+    "    abandonment 15\n",
+    "\n",
+    "A few things to note about the following command (but you don't need to memorize):\n",
+    "-  The `!` at the start of a line means to do an operating system command, not a Python command.\n",
+    "-  The `[ -e count_big.txt ] ||` part says to skip downloading the file if it already exists.\n",
+    "-  The `curl` command downloads the file\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 8,
+   "id": "4b0b245b-5085-492e-b3c3-902f2d8ae723",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "! [ -e count_big.txt ] || curl -O https://norvig.com/ngrams/count_big.txt"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "65006749-5475-434c-a6bb-aab8c81e6e0b",
+   "metadata": {},
+   "source": [
+    "I'll read the contents of the file into a Python dictionary, which will have the form `{'a': 21160, 'aah': 1, ...}`. "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 9,
+   "id": "c863b2e8-4e81-4c13-bd62-2aa7be38ad92",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "def make_dictionary(lines) -> dict:\n",
+    "    \"\"\"The lines are strings with a word and a frequency count; make it into a dict.\"\"\"\n",
+    "    counts = {} # Start with an emoty dict\n",
+    "    for line in lines:\n",
+    "        word, count = line.split()\n",
+    "        counts[word] = int(count)\n",
+    "    return counts\n",
+    "\n",
+    "dictionary = make_dictionary(open('count_big.txt'))"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "a5939c3b-b99a-4e8d-9cf5-9f4e8eb1533f",
+   "metadata": {},
+   "source": [
+    "Here are some things you can do with the dictionary:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 10,
+   "id": "9edff66d-8668-4408-b636-a2aec0614fcb",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "True"
+      ]
+     },
+     "execution_count": 10,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "'aback' in dictionary"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 11,
+   "id": "cae82016-a5d1-4fac-9e4d-75029e506f67",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "True"
+      ]
+     },
+     "execution_count": 11,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "'the' in dictionary"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 12,
+   "id": "8bf5eb96-7502-4568-bba0-71313f481e99",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "False"
+      ]
+     },
+     "execution_count": 12,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "'xyzzy!@#$' in dictionary"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 13,
+   "id": "5cbaf8af-a4eb-4390-b0f2-0bb0e32426ca",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "80030"
+      ]
+     },
+     "execution_count": 13,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "dictionary['the'] # get the frequency count"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 14,
+   "id": "d1919007-f2e6-484a-a078-c9dd805a17c2",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "80030"
+      ]
+     },
+     "execution_count": 14,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "dictionary.get('the', 0) # Get the count, with a default of 0 if word is not in dictionary"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 23,
+   "id": "b137e272-9f34-4ecc-9131-934304a4f5b2",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "0"
+      ]
+     },
+     "execution_count": 23,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "dictionary.get('xyzzy!@#$', 0) # Get the count, with a default of 0 if word is not in dictionary"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 15,
+   "id": "5e10a770-0945-48c7-ad37-826f2e42a2b1",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "29136"
+      ]
+     },
+     "execution_count": 15,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "len(dictionary) # the number of words in the dictionary"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "3662284a-b83e-4122-9896-831fc8580a87",
+   "metadata": {},
+   "source": [
+    "Now I want to take a pattern  and figure out the most likely word (which I will guess is the most frequent one):"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 16,
+   "id": "fea1a704-ab79-4204-bd89-506e66c12042",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "def most_likely_word(pattern: list[set[str]]) -> str:\n",
+    "    \"\"\"Out of all the possible words the pattern can make, pick the most frequent one.\"\"\"\n",
+    "    return max(possible_words(pattern), key=frequency)\n",
+    "\n",
+    "def frequency(word) -> int: \n",
+    "    \"\"\"The frequency count of the word in the dictionary, or 0 by default.\"\"\"\n",
+    "    return dictionary.get(word, 0) "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 17,
+   "id": "a7cbb472-ce03-4239-b64f-ee1f8cbe02e3",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'all'"
+      ]
+     },
+     "execution_count": 17,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "most_likely_word([b&v, a&t&c, a&t&c])"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "d78f5702-9064-4a50-822e-f6ad89a16497",
+   "metadata": {},
+   "source": [
+    "So far, so good!\n",
+    "\n",
+    "A puzzle consists of a list of word patterns, and we can generate a best guess at solving the puzzle by finding the `most_likely_word` for each word pattern, and then joining them into a big string."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 18,
+   "id": "b6f70f1d-5f16-4d80-bb95-fc8b01ab57df",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "def solve(puzzle: list[list[set[str]]]) -> str:\n",
+    "    \"\"\"Given a puzzle (a list of word patterns), return a string formed from the most likely matching words.\"\"\"\n",
+    "    return ' '.join(most_likely_word(pattern) for pattern in puzzle)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "316692e0-244f-4715-bec9-f6e7babcd036",
+   "metadata": {},
+   "source": [
+    "## Puzzle #3\n",
+    "\n",
+    "We're ready to see if our program can solve the puzzle:\n",
+    "\n",
+    "![](https://i.guim.co.uk/img/media/dd62fe8dfdc6eb9d98815a2e14791ae268aa4d46/0_0_580_75/master/580.jpg?width=310&dpr=2&s=none&crop=none)\n",
+    "\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 19,
+   "id": "42054f45-a8af-4513-a5d0-f097b2acda02",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'all the world ’ s a stage'"
+      ]
+     },
+     "execution_count": 19,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "solve(puzzle3)                                 "
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "8e3b7a2a-259c-463f-b542-5c095c559516",
+   "metadata": {},
+   "source": [
+    "It worked! Let's do another one:\n",
+    "\n",
+    "## Puzzle #1\n",
+    "\n",
+    "![](https://i.guim.co.uk/img/media/a54abfc70c03cf9bc40e178c4e6186915b97ea1e/0_0_580_75/master/580.jpg?width=310&dpr=2&s=none&crop=none)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 20,
+   "id": "688d1a5c-2770-4dd1-b8db-5d535949f909",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'all ’ s well that ends well'"
+      ]
+     },
+     "execution_count": 20,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "solve([[b&v, a&t&c, a&t&c], [{\"’\"}], [b&c], [w&c, b&v, t&c, t&c], [a&c, a&c, b&v, a&c], [b&v, b&c, a&c, b&c], [w&c, b&v, t&c, t&c]])"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "47db30ff-a96a-47d7-a4a0-34fe29dad4db",
+   "metadata": {},
+   "source": [
+    "That's correct!\n",
+    "\n",
+    "## Puzzle #8\n",
+    "\n",
+    " ![](https://i.guim.co.uk/img/media/3eba3f724bda55abf76c8bca57f645cd5a669aef/0_0_580_75/master/580.jpg?width=310&dpr=2&s=none&crop=none)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 21,
+   "id": "599ece2f-88a2-4818-83f9-0d0e478986ab",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'all roads lead to some'"
+      ]
+     },
+     "execution_count": 21,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "solve([[v, a&c, a&c], [b&n&c, b&n&v, b&n&v, a&c, b&c], [a&t&c, b&v, b&v, a&c],[a&c, b&v], [c, b&v, w&b&c, b&v]])"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "bfd1dc29-5958-4c51-a124-b39d633ea60f",
+   "metadata": {},
+   "source": [
+    "OK, not quite right, but a good hint.\n",
+    "\n",
+    "One more:\n",
+    "\n",
+    "## Puzzle #10\n",
+    "\n",
+    "\n",
+    "![](https://i.guim.co.uk/img/media/c358352e9f14f1fb0d0f458f034bb86777efcc83/0_0_464_75/master/464.jpg?width=310&dpr=2&s=none&crop=none)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 22,
+   "id": "68d34678-7688-49c4-94b6-5ba207497866",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'have in blind'"
+      ]
+     },
+     "execution_count": 22,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "solve([[a&c, b&v, b&c, b&v], [a&v, b&c], [a&c, a&t&c, a&v, b&c, a&c]])"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "87eb56d5-9a6b-41f0-8eec-b4c8f63dbdbd",
+   "metadata": {},
+   "source": [
+    "That's not right either, but again it is a good clue to the right answer. (One reason I didn't get this one right is that I didn't consider capital letters, and a Capital \"L\" has a different shape than a lowercase \"l\".)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "747c3d08-c98a-497d-9430-f6a69dbd70cc",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python [conda env:base] *",
+   "language": "python",
+   "name": "conda-base-py"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.13.9"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}

py/pytudes.py

@@ -57,13 +57,14 @@ notebooks = {
 ('How to Count Things', 2020, 'How%20To%20Count%20Things.ipynb', 'Combinatorial math: how to count how many things there are, when there are a lot of them'),
 ('KenKen (Sudoku-like Puzzle)', 2021, 'KenKen.ipynb', 'A Sudoku-like puzzle, but with arithmetic.'),
 ('Number Bracelets Game', 2024, 'NumberBracelets.ipynb', 'A game involving numbered beads on a circular bracelet.'),
+('Project Euler #3: Largest prime factor', 'Euler3.ipynb', 2026, 'Find the largest prime factor of a number'),
 ('Pairing Socks', 2019, 'Socks.ipynb', 'What is the probability that you will be able to pair up socks as you randomly pull them out of the dryer?'),
 ('Sicherman Dice', 2018, 'Sicherman%20Dice.ipynb', 'Find a pair of dice that is like a regular pair of dice, only different'),
 ("Sol Golomb's Rectangle Puzzle", 2014, 'Golomb-Puzzle.ipynb', 'A Puzzle involving placing rectangles of different sizes inside a square'),
 ("Stubborn number endings", 2024, 'Stubborn.ipynb', 'Any number ending in 5 has a square that also ends in 5. What other endings are like this?'), 
 ('Star Battle (Sudoku-like Puzzle)', 2021, 'StarBattle.ipynb', 'Fill-in-the-grid puzzle similar to Sudoku'),
 ('Sudoku', 2006, 'Sudoku.ipynb', 'Classic fill-in-the-grid puzzle'),
-('Sudoku: 100,000 puzzles/second in Java', 2021, 'SudokuJava.ipynb', 'A version of the Sudoku solver using parallel threads and other optimizations'),
+('Sudoku: 200,000 puzzles/second in Java', 2021, 'SudokuJava.ipynb', 'A version of the Sudoku solver using parallel threads and other optimizations'),
 ('Square Sum Puzzle', 2020, 'SquareSum.ipynb', 'Place the numbers from 1 to n in a chain (or a circle) such that adjacent pairs sum to a perfect square'),
 ("When is Cheryl's Birthday?", 2020, 'Cheryl.ipynb', "Solving the *Cheryl's Birthday* logic puzzle"),
 ('When Cheryl Met Eve: A Birthday Story', 2015, 'Cheryl-and-Eve.ipynb', "Inventing new puzzles in the Style of Cheryl's Birthday"),
@@ -74,6 +75,7 @@ notebooks = {
 'Word Puzzles': [
 ('Boggle / Inverse Boggle', 2020, 'Boggle.ipynb', 'Find all the words on a Boggle board; then find a board with a lot of words'),
 ('Chemical Element Spelling', 2020, 'ElementSpelling.ipynb', 'Spelling words using the chemical element symbols, like CoIn'),
+('Did you solve it? R y clvr ngh t rd ths sntnc?', 2026, 'clvr.ipynb', 'Guess famous phrases from letter shapes. Beginner level.'),
 ('Equilength Numbers: FOUR = 4', 2020, 'equilength-numbers.ipynb', 'What number names have the same letter count as the number they name (such as FOUR)?'),
 ('Gesture Typing', 2017, 'Gesture%20Typing.ipynb', 'What word has the longest path on a gesture-typing smartphone keyboard?'),
 ('Ghost: A Word game', 2017, 'Ghost.ipynb', 'The word game Ghost (add letters, try to avoid making a word)'),
@@ -203,7 +205,6 @@ def format_notebook(title, year, url, comment=''):
     nb = f'[N](https://nbviewer.jupyter.org/github/norvig/pytudes{urlb})'
     sm = f'[S](https://studiolab.sagemaker.aws/import/github/norvig/pytudes{urlb})'
     ti = f'<a href="{gh[4:-1]}" title="{comment}">{title}</a>'
-    if year == current_year: year = f'<u>{year}</u>'
     return f'| {co} {dn} {my} {nb} {sm} | {year} | {ti} |'
 
 def format_pythons() -> str: