number-munchers/sass/board/board.scss

.board {
    margin:0 auto;
    position:relative;
    width:600px;

    @for $i from 0 through 6 {
        .x#{$i} {
            left: #{$i * 100}px;
        }

        .y#{$i} {
            top: #{$i * 100}px;
        }
    }
}