* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    height: 100vh;
}

#instruction {
    position: absolute;
    height: 80%;
    width: 90%;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background-color: rgba(0, 0, 0, 0.829);
    border-radius: 25px;
    color: rgb(28, 188, 0);
    z-index: 1;
    transition: all 1s ease-in-out;


}

#Name_input {
    margin-top: 3%;
    justify-self: center;
}

label {
    font-size: larger;

}

#level_op {
    margin-top: 1%;
    justify-self: center;
}

h1 {
    padding: 2%;
    text-align: center;
}

ol {
    padding: 2%;
    margin-left: 3%;
}

li {
    margin-top: 1%;
    color: whitesmoke;
    font-size: larger;
}

button {
    position: absolute;
    top: 80%;
    left: 42%;
    height: 10%;
    width: 15%;
    background-color: rgba(28, 188, 0, 0.718);
    color: aliceblue;
    font-size: larger;
    border-radius: 10px;
    border: none;
}

#small_nav {
    display: none;
    justify-content: space-between;
    font-size: x-large;
    padding-top: 1%;
    padding-left: 2.5%;
    padding-right: 2.5%;
}

nav {
    background-color: rgb(24, 168, 235);
    height: 10vh;
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    align-items: center;
    text-align: center;
    font-size: x-large;
    color: aliceblue;

}

nav div {
    display: flex;
}

#score_board {
    justify-content: end;
    margin-right: 8%;


}

#high_score {
    margin-left: 8%;
}

#Level_board {
    justify-content: center;
}

#container {
    height: 500px;
    width: 500px;
    border-radius: 20px;
    box-shadow: 0 0 20px rgba(0, 0, 0, 0.603);
    position: absolute;
    top: 51%;
    left: 50%;
    transform: translate(-50%, -50%);
}

#wrapper {
    height: 90%;
    width: 90%;
    display: grid;
}

.box {
    height: 100%;
    width: 100%;
    box-shadow: 0 0 5px rgba(0, 0, 0, 0.603);
    border-radius: 10px;
    background-color: rgb(255, 255, 255);
    transform-style: preserve-3d;
    transition: transform 0.5s ease;
}

.front_side,
.back_side {
    object-fit: contain;
    height: 80%;
    position: absolute;
    top: 50%;
    left: 50%;
    transform-style: preserve-3d;
    transition: opacity 0.5s ease-in-out;
    transform: translate(-50%, -50%);
}

.front_side {
    opacity: 1;
    width: 80%;

}

.back_side {
    opacity: 0;
    top: 10%;
    left: 30%;
    transform: rotateY(180deg);
}

#end-page {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    z-index: 2;
    height: 50%;
    width: 50%;
    background-color: rgba(68, 64, 64, 0.707);
    border-radius: 10px;
    display: none;
}

#play-again-btn {
    position: relative;
    top: 60%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 30%;
}

#end-content {
    color: aliceblue;
    height: 15%;
    padding-top: 10%;
    text-align: center;
}

#end-score {
    padding-top: 3%;
}

.easy-level {
    margin-left: 5%;
    margin-top: 3%;
    grid-template-columns: repeat(4, 23.3%);
    grid-template-rows: repeat(2, 46.6%);
    row-gap: 10px;
    column-gap: 10px;

}

.medium-level {
    margin-left: 5%;
    margin-top: 5%;
    grid-template-columns: repeat(4, 23.3%);
    grid-template-rows: repeat(4, 23.3%);
    row-gap: 10px;
    column-gap: 10px;
}

.hard-level {
    margin-left: 5%;
    margin-top: 5%;
    grid-template-columns: repeat(6, 15%);
    grid-template-rows: repeat(6, 15%);
    row-gap: 10px;
    column-gap: 10px;

}

.matched {
    pointer-events: none;
}

.flip {
    transform: rotateY(180deg);

    .front_side {
        opacity: 0;
    }

    .back_side {
        opacity: 1;
        transform: rotateY(180deg);
    }
}

.unflip {
    .front_side {
        opacity: 1;

    }

    .back_side {
        opacity: 0;
    }
}

.reduce {
    opacity: 0;
    overflow: hidden;
    visibility: hidden;
}



@media only screen and (max-width: 600px) {
    nav {
        padding-top: 30px;
    }

    button {
        width: 30%;
        height: 5%;
        position: absolute;
        top: 80%;
        left: 50%;
        transform: translate(-50%, -50%);
    }

    ol {
        margin-left: 5%;
    }

    h1 {
        padding-top: 5%;
    }

}

#timer {
    position: absolute;
    top: 37.5%;
    left: 10%;
    height: 25vh;
    width: 25vh;
    background-color: rgba(24, 168, 235, 0.664);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 0 20px rgba(0, 0, 0, 0.603);
    transition: all 0.5s ease;
}

#seconds {
    color: aliceblue;
    font-size: 600%;
    font-weight: 400;
}