style.css

@import url('https://fonts.googleapis.com/css2?family=Russo+One&display=swap');

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

.game-cover {
    background: url("http://i1.faceprep.in/prograd-junior/numeron-bg.png") no-repeat;
    background-size: cover;
}

body {
    font-family: 'Russo One', sans-serif;
    color: white;
    height: 100vh;
    flex-direction: column;
}

.flex-centered {
    display: flex;
    align-items: center;
    justify-content: space-evenly;
}

.game {
    background: url("http://i1.faceprep.in/prograd-junior/game-inside-bg.png") no-repeat;
    background-size: cover;
}

#logo {
    width: 80%;
    height: auto;
}

.play {
    width: 180px;
    cursor: pointer;
}

#numbers {
    width: 100%;
    display: flex;
    justify-content: space-around;
    align-items: center;
}

.number-holder {
    background-color: white;
    color: black;
    width: 25vw;
    max-width: 200px;
    max-height: 200px;
    height: 25vw;
    border: 2px solid #EE2689;
}

#instructions {
    font-size: 6vw;
}

#numbers * {
    font-size: 4vw;
}

#buttons * {
    width: 25%;
    min-width: 120px;
    cursor: pointer;
}

#timer {
    width: 10%;
    position: absolute;
    top: 5vh;
    right: 5vh;
    font-size: 6vw;
    border: 1px solid white;
    border-radius: 3px;
}

#game-over-text {
    width: 50%;
    max-width: 500px;
}

#score-box {
    font-size: 6vw;
    border: 1px solid white;
    padding: 2vw;
}

.operators {
    font-size: 3em;
    border: 1px solid #ee2689;
    padding: 30px;
    text-align: center;
    background-color: white;
    color: black;
    margin-right: 100px;
    border-radius: 50%;
}

#buttons {
    display: flex;
    justify-content: space-evenly;
}