Wildlife Sudoku (Flagdoku)

Wildlife is a daily animal puzzle from Flagdoku, the site best known for its flag grid. It works like an immaculate-grid quiz: there are three categories across the top and three down the side, and every cell needs an animal that fits both its row and its column.

Categories mix biology, habitat and spelling. One day's grid, for example, asked for animals whose name contains an O, fish, and sea creatures across the top, against animals starting with S, animals with scales and predators down the side. You search for an animal by name and drop it into a cell; clicking a category shows its exact criteria.

Each correct animal scores a point, up to nine, and wrong animals score nothing. There is also an answer of the day that fits all the categories for a bonus. Past grids can be played from the archive by number.

It is free, needs no account and plays in the browser, with ads on the page. A hint button in each cell's search box, a hard mode and a share card that shows how rare your answers were add to the basic grid. It suits nature fans and quiz players who like grid puzzles where several answers can be right.