* { box-sizing: border-box;  } 

body {
    background: #fff;
    color: #333;
    font-family: 'Open Sans', sans-serif;
    font-size: 16px;
    line-height: 24px;
    font-style: normal; 
}

#content {
    position: relative;
    width: 960px;
    margin: 50px auto;
    box-shadow: 5px 6px 10px 1px rgba(192,192,192,0.2);
    text-align: center;
    padding: 50px 0;
}

h2 {
    color: #3d4045;
    text-transform: uppercase;
    font-size: 1.8rem;
}

p {
    font-size: 1.3rem;
}

#plateau {
    border: 1px solid #ccc;
    border-collapse: collapse;
    text-align: center;
    margin: 0 auto;
}

#plateau td {
    width: 150px;
    height: 150px;
    margin: 0px;
    padding: 0px;
    border: 1px solid #ccc;
    cursor: pointer;
    position: relative;
}

#plateau td:before, #plateau td:after {
    position: absolute; 
    left: 10%;
    content: "";
    width: 80%;
}

#plateau td.joueur1:after {
    transform: rotate(135deg);
    border: 3px solid #3d4045;
    transition: transform 0.3s;
}

#plateau td.joueur1:before {
    transform: rotate(-135deg);
    border: 3px solid #3d4045;
    transition: transform 0.3s;
}

#plateau td.joueur2:after {
    border-radius: 50%;
    width: 70%;
    height: 70%;
    background: #3d4045;
    top: 15%;
    left: 15%;
    transition: background 0.3s;
}

.visible {
    display: block;
}

.hidden {
    display: none;
}

#overlay {
    background-color: rgba(42, 50, 75, 0.9);
    position: fixed;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    z-index: 5;
}

#message {
    position: absolute;
    width: 350px;
    background: #fff;
    top: 35%;
    transform: translate(-50%);
    left: 50%;
    padding: 30px;
    text-align: center;
}

#replay {
    border: 1px solid rgb(218,36,72);
    background: #fff;
    padding: 15px 30px;
    color: rgb(218,36,72);
    border-radius: 8px;
    cursor: pointer;
    font-size: 1.2rem;
    transition: background 0.3s;
    outline: none;
}

#replay:hover {
    background: rgb(218,36,72);
    color: #fff;
}

@media only screen and (max-width: 960px) {
    #content {
        width: 90%;
        padding: 10px 0;
        margin-top: 10px;
    }

    #plateau {
        width: 90%;
    }

    #plateau td {
        width: 30%;
    }

    #plateau td:before, #plateau td:after {
        left: 20%;
        content: "";
        width: 60%;
    }

    #plateau td.joueur2:after {
        border-radius: 50%;
        width: 50%;
        height: 50%;
        top: 25%;
        left: 25%;
    }
}