However, wait! Our game can only work if the same color appears in only two cells: a cell and its twin cell. Moreover, a cell can be hidden or not: can the color be seen or not? To take care of this, the Cell class gets two new attributes:
Cell twin; bool hidden = true;
Note
For the code files of this section, refer to Chapter 7\code\educ_memory_game\spirals\s04 in the code bundle.
The _colorBox method in the Board class can now show the color of the cell when hidden is false (line (2)); when hidden = true (the default state), a neutral gray color will be used for the cell (line (1)):
static const String COLOR_CODE = '#f0f0f0';
We also gave the gap variable a better name, boxSize:
void _colorBox(Cell cell) {
var x = cell.column * boxSize;
var y = cell.row * boxSize;
context.beginPath();
if (cell.hidden) {
context.fillStyle = COLOR_CODE; (1)
} else {
context.fillStyle = colorMap[cell.color]; (2...