getSvgChessboard() {
// NOTE: with small margin seems nicer
let width = 173.2 * this.size.y + 173.2 * (this.size.y-1) / 2 + 30,
height = 50 + Math.floor(150 * this.size.x) + 30,
min_x = -86.6 - 15,
min_y = -100 - 15;
getSvgChessboard() {
// NOTE: with small margin seems nicer
let width = 173.2 * this.size.y + 173.2 * (this.size.y-1) / 2 + 30,
height = 50 + Math.floor(150 * this.size.x) + 30,
min_x = -86.6 - 15,
min_y = -100 - 15;