Cross constructor

Cross()

It creates a 6x6 matrix of zeros

Implementation

Cross() {
  grid = <List<int>>[
    <int>[0, 0, 0, 0, 0, 0],
    <int>[0, 0, 0, 0, 0, 0],
    <int>[0, 0, 0, 0, 0, 0],
    <int>[0, 0, 0, 0, 0, 0],
    <int>[0, 0, 0, 0, 0, 0],
    <int>[0, 0, 0, 0, 0, 0],
  ];
}