In the game Shakashaka, players create white "rooms" surrounded by black borders in either an upright direction, or angled at 45 degrees (see Rules tab). The black edges of these rooms and be created using either the mouse or keyboard keys:

• A left-click on a white cell toggles through 5 potential settings for the cell (one of 4 black triangles, or empty; the rules do not allow for adding a pure black cell).
• The rotation of states starts with a black triangle in the NE corner, then rotating SE, SW, NW, then back to white. That is ◥ → ◢ → ◣ → ◤ → white.
• Alternately you can use arrow keys to move around the board, and press the space bar to toggle through the options, or
• Press number keys '1' - '4' to set a triangle in the corresponding corner (starting with '1' for NE ◥ and moving clockwise to '4' for ◤), or
• Press '0' or the backspace key to return to white.
• You can right-click or press the '.' key to put a dot place-holder for a cell that, by your determination, must stay white.

In Assist Mode (0), the default, only the existance of errors or incomplete numbered cells is indicated. In Assist Mode (1), the number of errors and incomplete cells is indicated, see game rules. In Assist Mode (2), errors and completed number are highlighted with colors. In some cases the solve difficulty will greatly decrease in Assist Mode (2), so select depending upon the level of challenge desired. The game border will turn green if the grid is completed without error. You can click the "undo" button on the bottom of the page to undo previous moves.

Below, enter puzzle code (0-0) for one of a list of pre-defined puzzles, or a puzzle descriptor (see "Puzzles" tab). Puzzle code 0 shows an example completed puzzle that can be helpful. The following puzzle codes have demos, which will walk you through a solve to help you on the path to mastery: []).

Shakashaka (シャカシャカ) is a unique Japanese logic puzzle published by Nikoli. In Shakashaka, the board begins with a number of black squares, some with numbers, and some without. The goal is to paint some of the white cells with triangles in one of the four corners of the cell, that is ◥ ◢ ◣ or ◤. A cell can't be set to be completely black, but can be left white. The rules below apply to these numbered cells and the triangular cells.

1. A black square with a number indicates how many triangles must be horizontally or vertically adjacent to it.
2. A black square with no number has an unconstrained number of triangles adjacent to it.
3. To complete the board, all white spaces must be creating a rectangular shape. That is, a rectangular combination of white squares, or a combination of white squares and white portions of triangular cells that forms a rectangle of any size.

Enter puzzle #0 in the tab below to see a completed puzzle.

Puzzles can be invoked by either a numerical entry from 0-0, or through a character description of the puzzle itself, entered into the Display form on the 'Game Play' tab. The numbered puzzles are hand-crafted of varying difficulty, roughly easy to hard. Puzzle 0 shows a completed correct puzzle.

To describe a puzzle, the character string must be of the form: "WxH:<descriptor>", where W is a number indicating the width of the grid, and H the height. The descriptor is a list of the black squares with numbers 0-4, or a '*' for a black square without a digit, from left to right, then top to bottom. To assist in the definition of a sparse board, a combination of b consecutive white squares can be represented with a lowercase letter from 'a' to 'z', corresponding to 1 to 26 consecutive squares. A dot '.' can be used as a visual separator, for example between rows. An example descriptor is as follows for entry 1: 'descr'.

For Shakashaka there are 1 demo puzzles that can be helpful to walk through solving methods. They are puzzle codes []. Enter them in the Game Play tab with the code number and there will be added a demo panel to help with the solve.

This playground was written using javascript and is available open source. All code is checked into the github repo at ohmec/puzzles. Feel free to file bugs there!