:root {
    --c-board-first: #fff;
    --c-board-second: #000;

    --c-piece-first-border: #C6C5C5;
    --c-piece-first-main: #F9F4F4;
    --c-piece-first-inner: #DBD8D8;

    --c-piece-second-border: #BAB9B9;
    --c-piece-second-main: #2B2B2B;
    --c-piece-second-inner: #181818;
}


body {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;

    background: grey;
}

.main {
    display: flex;
    flex-direction: column;
    align-items: center;
    flex-grow: 1;
}

.container {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 1rem;
    flex-grow: 1;
}

.board {
    --board-width: 0;
    --board-height: 0;
    --cell-size: 0;

    width: calc(var(--cell-size) * var(--board-width));
    height: calc(var(--cell-size) * var(--board-height));
    display: flex;
    flex-direction: column;
    align-items: stretch;

    border-radius: .5rem;
    border: .5rem solid var(--c-board-first);
    box-shadow: 0 0 0 .25rem var(--c-board-second),
    0 2.25rem 2.5rem -.25rem var(--c-board-second),
    0 2rem 0 .25rem var(--c-board-second);

    position: relative;
}

.board__row {
    display: flex;
    align-items: stretch;
    flex-grow: 1;
}

.board__row:nth-child(2n) {
    flex-direction: row-reverse;
}

.board__cell {
    background: var(--c-board-first);
    flex-grow: 1;
}

.board__cell:nth-child(2n) {
    background: var(--c-board-second);
}

.board__cell_highlighted {
    position: relative;
}

.board__cell_highlighted:after {
    content: '';

    width: 100%;
    height: 100%;
    box-sizing: border-box;

    border: .5rem solid green;

    position: absolute;
    top: 50%;
    left: 50%;
    translate: -50% -50%;
}


.piece {
    --main-color: var(--c-piece-first-main);
    --border-color: var(--c-piece-first-border);

    width: calc(var(--cell-size) * .9);
    height: calc(var(--cell-size) * .9);
    box-sizing: border-box;
    border-radius: 100%;
    border: calc(var(--cell-size) * .05) solid var(--border-color);
    background: var(--main-color);

    position: absolute;
    translate: calc(var(--cell-size) * .05) calc(var(--cell-size) * .05);

    transition: .25s ease;
    transition-property: box-shadow, top, left;
    box-shadow: 0 0 0 var(--main-color);
}

.piece:before {
    content: '';

    width: 60%;
    height: 60%;
    border-radius: 100%;
    border: calc(var(--cell-size) * .025) solid var(--border-color);
    background: var(--main-color);

    position: absolute;
    top: 50%;
    left: 50%;
    translate: -50% -50%;
}

.piece_second-team {
    --main-color: var(--c-piece-second-main);
    --border-color: var(--c-piece-second-border);
}

.piece__hover {
    box-shadow: 0 0 1.5rem .25rem var(--main-color);
}