Daydoku

Daydoku takes the wooden calendar puzzle and puts it in the browser. The main board has a grid of months, day numbers and weekdays, and ten pieces (three tetrominoes and seven pentominoes). The day's challenge is to fit all of them inside the calendar so that the only squares left uncovered are today's month, day and weekday. Because the target is the date, every player is solving the same challenge on the same day.

There are five boards, each with its own challenge per day. Micro is a compact two-window board with 11 tiny pieces. Classic is the familiar two-window board with 9 pieces that leaves only the month and day. Mini is a year-planner layout cut into 14 small triominoes and tetrominoes. Grande uses just 8 big pieces, pentominoes and a hexomino, and is the hardest. The site says every board has been checked by computer to have at least one solution for every date of the year, and most dates have many.

Pieces start scattered around the board. You drag them on, rotate them with the ring around a selected piece, and flip non-symmetrical ones with a button. Pieces snap to the grid when dropped.

It suits fans of pentomino and tangram puzzles and anyone who likes a hands-on spatial puzzle rather than a word or number game.