To play, click on a cell to switch between light, dark, and the default indeterminate state. A left-click turns it black, a right-click turns to white, and a middle-click returns to indeterminate. Once the mouse is pressed down, you can drag the mouse to set multiple squares in one sequence. Alternately, you can use the arrow keys to move around the board, and press the space bar to toggle between the states, or the '1' key to turn black, the '0' key to turn white, or the backspace key to set back to indeterminate.

In Assist Mode (0), the default, only the existance of errors or incomplete rooms is indicated. In Assist Mode (1), the number of errors and incomplete rooms is indicated, see game rules. In Assist Mode (2), errors and completed rules are highlighted with digit colors. In some cases the solve difficulty will greatly decrease in Assist Mode (2), so select depending upon the level of challenge desired. The canvas border will turn green if the grid is completed without error. You can press 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). The following puzzle codes have demos, which will walk you through a solve to help you on the path to mastery: []).

Choco Banana (チヨコバナナ) is one of the newer Japanese logic puzzle published by Nikoli. In Choco Banana, the puzzle board is initiated with some numbers that must be separated into collections of squares, or rooms, that contain the number of squares of that number. Sometimes rooms must be created without knowing in advance how many squares are contained. The following rules relate to these numbers and the size and shape of the rooms that must be created.

1. A number indicates the number of cells of the area containing this cell.
2. Black cells must form a rectangle when linked with their neighbors. I.e. a collection of contiguous black cells could be of combined size 2x3, or 1x4, or 1x1, etc. If it contains a number it must be that combined size. For example a black room with the number three could be a 1x3 or 3x1 collection of black squares.
3. White cells must not form a rectangle when linked with their neighbors. For example a white room with the number three could only be an L-shape collection of three white cells, though they could be in any orientation.
4. Rooms, or collections of cells, do not need to contain a number.

Below select puzzle 0 to see a completed sample grid. See the Game Play or Puzzles tab for how to invoke a demo.

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:<digit-descriptor>", where W is a number indicating the width of the grid, and H the height. The digit descriptor is a list of the pre-defined digit contents, from left to right, then top to bottom. Blank cells are represented with a '-' character. To assist in the definition of a sparse board, a combination of b consecutive blanks can be represented with a lowercase letter from 'a' to 'z', corresponding to 1 to 26 consecutive blanks. Digit values greater than '9' should be represented with capital letters 'A' to 'Z' representing 10 to 35. A dot '.' can be used as a visual separator, for example between rows. An example descriptor is as follows for entry 1: 'descr'.

For Choco Banana 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!