newGame method
Implementation
void newGame(int size) {
const baseUrl = 'https://loremflickr.com/200/200?lock=';
final random = Random();
final baseList = List.generate(
(size * size / 2).floor(),
(_) => '$baseUrl${random.nextInt(5000)}',
);
final items = [
...baseList,
...baseList,
if (size % 2 == 1) null,
]..shuffle();
state = CouplesState(
size: size,
items: items,
isLoading: false,
);
}