/*---[ MAIN ]---*/
*, *::after, *::before {
    box-sizing: border-box;
}

:root {
    --cell-size: 100px;
    --mark-size: calc(var(--cell-size) * .9);
    --background-color: black;
    --main-color: white;
}

body {
    margin: 0;
    background-color: var(--background-color);
}

/*---[ Winner message ]---*/
.winner {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: rgba(0, 0, 0, .9);
    justify-content: center;
    align-items: center;
    color: var(--main-color);
    font-size: 5rem;
    font-family: Arial, sans-serif;
    flex-direction: column;
}

.winner button {
    font-size: 3rem;
    background-color: var(--background-color);
    color: var(--main-color);
    border: 1px solid var(--main-color);
    padding: .25em .5em;
    cursor: pointer;
}

.winner button:hover {
    background-color: var(--main-color);
    color: var(--background-color);
    border-color: var(--background-color);
}

.winner.show {
    display: flex;
}

/*---[ Board styling ]---*/
.board {
    width: 100vw;
    height: 100vh;
    display: grid;
    justify-content: center;
    align-content: center;
    justify-items: center;
    align-items: center;
    grid-template-columns: repeat(3, auto);
}

/*---[ Cell styling ]---*/
.cell {
    width: var(--cell-size);
    height: var(--cell-size);
    justify-content: center;
    align-items: center;
    display: flex;
    background-color: var(--background-color);
    border: 2px solid var(--main-color);
    position: relative;
    cursor: pointer;
}

.cell.x,
.cell.o {
    cursor: not-allowed;
}

/*---[ Remove edge border for edge cells ]---*/
.cell:nth-child(1),
.cell:nth-child(2),
.cell:nth-child(3) {
    border-top: none;
}

.cell:nth-child(1),
.cell:nth-child(4),
.cell:nth-child(7) {
    border-left: none;
}

.cell:nth-child(3),
.cell:nth-child(6),
.cell:nth-child(9) {
    border-right: none;
}

.cell:nth-child(7),
.cell:nth-child(8),
.cell:nth-child(9) {
    border-bottom: none;
}

/*---[ X ]---*/
.cell.x::before,
.cell.x::after {
    content: '';
    position: absolute;
    width: calc(var(--mark-size) * .1);
    height: var(--mark-size);
    background-color: var(--main-color);
}

.board.x .cell:not(.x):not(.o):hover::before,
.board.x .cell:not(.x):not(.o):hover::after {
    content: '';
    position: absolute;
    width: calc(var(--mark-size) * .1);
    height: var(--mark-size);
    background-color: dimgray;
}

.cell.x::before,
.board.x .cell:hover::before {
    transform: rotate(45deg);
}

.cell.x::after,
.board.x .cell:hover::after {
    transform: rotate(-45deg);
}

/*---[ O ]---*/
.cell.o::before,
.cell.o::after {
    content: '';
    position: absolute;
    border-radius: 50%;
    width: var(--mark-size);
    height: var(--mark-size);
    background-color: var(--main-color);
}

.board.o .cell:not(.x):not(.o):hover::before,
.board.o .cell:not(.x):not(.o):hover::after {
    content: '';
    position: absolute;
    border-radius: 50%;
    width: var(--mark-size);
    height: var(--mark-size);
    background-color: dimgray;
}

.cell.o::before {
    height: calc(var(--mark-size) * .9);
    width: calc(var(--mark-size) * .9);
    background-color: var(--main-color);
}

.board.o .cell:not(.x):not(.o):hover::before {
    height: calc(var(--mark-size) * .9);
    width: calc(var(--mark-size) * .9);
    background-color: dimgray;
}

.cell.o::after,
.board.o .cell:not(.x):not(.o):hover::after{
    height: calc(var(--mark-size) * .69);
    width: calc(var(--mark-size) *.69);
    background-color: var(--background-color);
}