Very pretty looking game. The Minesweeper element is far too easy and there is an autoplay feature which can be toggled with 'A' on your keyboard.
The map, I think, is infinite. I scrolled left for about 10 minutes making new land and there was no end in sight.
It would be nice to have an English translation of things - instructions, hints and map markers - as my Japanese is about as good as my Sanskrit. Maybe there's a much-needed difficulty setting, but I wouldn't know.
But all in all an aesthetically pleasing game to watch.
EDIT: I think the main menu is the difficulty setting - Sort of Easy, Medium, Hard - but more like, very easy, easy, not so easy.