Blueberry

Blueberry presents a nine-by-nine grid, gray, dotted with a point at the center of each cell, and divided into regions with thick borders. Three sets of clues intersect on it: a number for each row, a number for each column and a number for each region, each indicating how many cells must be filled within its perimeter. The current date is written beneath the title, and the bottom bar lines up Reset, Undo, Redo and Check.

1. Read the three sets of clues: the left column for the rows, the top row for the columns, and the small number tucked into the corner of each region.
2. Click the cells to place your marks.
3. Correct with Undo and Redo, or start over with Reset.
4. Use Check to settle it when the grid is complete.

Because three systems of clues on the same board mean a cell always belongs to three lines of reasoning at once. The freeform regions break the regularity of rows and columns and prevent the automatic reading you eventually develop on square grids. Everything is contained in an intentionally bare interface, without color or animation: just numbers, thick borders and a running timer.

The Check button is there for arbitration. What the browser retains says a lot about the game: the cell-by-cell state, the full command history for Undo and Redo, the time spent to the millisecond, and an indicator that records whether a clue has been used.

Daily

The tab opened by default, with the current date clearly shown beneath the title.

Grids 1, 2 and 3

Three numbered buttons next to the tabs, grid 1 being selected on opening.

Plus

A tab placed between Daily and the grid selector, grayed out.

• The sum of the row clues, the sum of the column clues and the sum of the region clues necessarily give the same total: it's a free check before placing the first mark, and a safety net when the grid gets stuck.
• Regions with zero are the best entry points: they can be cleared entirely at once and immediately open the rows and columns that cross them.
• The timer starts when the page loads, not on the first click: if time matters to you, prepare your reading before opening the tab.