In Double Choco, the goal is to draw border walls around cells to satisfy the goals of the game (see rules tab). To draw borders, you can use the mouse or arrow and button keys:

• A left-click on a border between cells creates a wall between cells
• A right-click on an existing wall removes it.
• You can mouse drag around to continue to draw the wall, or erase the wall.
• Once on a boundary, you can press the shift key and then arrow keys to add border walls in the direction of the arrow keys.
• Once on a wall, you can press the space bar to toggle the wall state, or press the '1' key to set, or '0' key or backspace to clear a wall.

In Assist Mode (0), the default, only the existance of errors or incomplete numbers is indicated. In Assist Mode (1), the number of errors and incomplete numbers is indicated, see game rules. In Assist Mode (1) or higher, each numbered square is given a different color to visually guide the solver in searching for room completions. In Assist Mode (2) errors are highlighted with cell colors, and correct completed rooms are indicated as well. Note this does not ensure that they are correct in the final solution, just that they are correct with respect to the rules. In some cases the solve difficulty will greatly decrease in Assist Mode (1) or higher, 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: []).

Double Choco (ダブルチョコ) is a newer Japanese logic puzzle published by Nikoli. In Double Choco, the board begins with half of the cells grayed out, and half white. Some cells have numbers. The contents of the cells can not be modified. Instead, the user must draw borders between cells in order to satisfy the set of rules below.

1. Draw borders around collections of cells containing an equal number of white cells and gray cells.
2. Cells with numbers in them indicate the number of white cells and gray cells that must be in the room that contains them. For instance, a cell with a '5' digit within it must eventually be in a room with 10 total cells: 5 white and 5 black.
3. A room can have more than one of the same number within, or no numbers.
4. Within a completed room, the two halves (white and gray) must be of the same shape; rotations and mirror images are OK. For instance, a '4' room could have one white 'L' shape "on its back" (⏗) and a gray one flipped and reversed (Γ). They must be touching horizontally or vertically.

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 Double Choco 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!