Mind Benders: 23 sites worth your time

Slide tiles, double numbers, lose an hour to one more go

Flood the whole board with one colour in thirty moves

Measure your reaction time against millions of strangers

Minesweeper with leaderboards and no Windows required

Tetris, except every block collapses into loose sand

Endless chess tactics drawn from real losing positions

Start with four elements, end with 700-odd absurd ones

Wordle for people who would rather guess an equation

Modern competitive stacking against real opponents

Swap letters until six words fall into place

One five-letter word a day, same word for everybody

Sixteen words, four secret groups, four mistakes allowed

Learn CSS flexbox by getting frogs onto lily pads

Numbers along the edges, a picture hiding in the grid

A daily puzzle page designed by people who love puzzles

Crosswords where every clue is a regular expression

Guess the word by meaning, not by letters

Forty small logic puzzles, endlessly generated, no fuss

The sudoku app built for puzzles with unusual rules

Every password rule you feared, plus a chess puzzle

One properly hard maths puzzle, every single month

Maths problems you solve by writing a bit of code

A whole site of people inventing puzzles for each other