*,*::after, *::before {
    box-sizing: border-box;
}

:root {
    --cell-size: 160px;
    --mark-size: calc(var(--cell-size)* .9);
}

body {
    margin: 0;
}

.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 {
    width: var(--cell-size);
    height: var(--cell-size);
    border: solid black 1px;
    background-color:white;
    display: flex;
    justify-content: center;
    align-items:center;
    position: relative;
    cursor: pointer;
}

.cell:first-child,
.cell:nth-child(2),
.cell:nth-child(3){
    border-top:none;
}

.cell:nth-child(3n + 1){
    border-left:none;
}

.cell:nth-child(3n + 3){
    border-right:none;
}

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

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

.cell.x::before,
.cell.x::after,
.cell.circle::before {
    background-color: black;
}

.board.x .cell:not(.x):not(.circle):hover::before,
.board.x .cell:not(.x):not(.circle):hover::after,
.board.circle .cell:not(.x):not(.circle):hover::before{
  background-color: lightgrey;
}

.cell.x::before,
.cell.x::after,
.board.x .cell:not(.x):not(.circle):hover::before,
.board.x .cell:not(.x):not(.circle):hover::after{
    content: '';
    position: absolute;
    width: calc(var(--mark-size) * .15);
    height: var(--mark-size); 
}

.cell.x::before,
.board.x .cell:not(.x):not(.circle):hover::before{
   transform:rotate(45deg)
}

.cell.x::after,
.board.x .cell:not(.x):not(.circle):hover::after {
    transform:rotate(-45deg)
 }

.cell.circle::before,
.cell.circle::after,
.board.circle .cell:not(.x):not(.circle):hover::before,
.board.circle .cell:not(.x):not(.circle):hover::after {
    content: '';
    position: absolute;
    border-radius: 50%;  
}

.cell.circle::before,
.board.circle .cell:not(.x):not(.circle):hover::before{
    width: var(--mark-size);
    height: var(--mark-size);
  
}

.cell.circle::after,
.board.circle .cell:not(.x):not(.circle):hover::after{
    width: calc(var(--mark-size) * .7);
    height: calc(var(--mark-size) * .7);
    background-color:white;
}


.winning-message {
    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: white;
    font-size: 5rem;
    flex-direction: column;
}

.winning-message button {
    font-size: 3rem;
    background-color: white;
    border:1px solid black;
    padding: .25em .5em;
    cursor: pointer;
}

.winning-message button:hover {
    background-color: black;
    color: white;
    border-color: white
}

.winning-message.show {
    display: flex;
}