index.css

* {
    -webkit-touch-callout:none;
    -webkit-user-select:none;
    -khtml-user-select:none;
    -moz-user-select:none;
    -ms-user-select:none;
    user-select:none;
}

body {
    color: #4495fb;
    margin: 0;
    padding: 0;
}

#jump_app {
    position: absolute;
    top: 0px;
    background-color: rgba(37, 42, 47, 0.6);
    height: 100%;
    width: 100%;
}

#jump_app > div:first-child {
    position: relative;
    margin: 12% auto 0;
    width: 450px;
    height: 450px;
    max-width: 100%;
    background-color: rgba(37, 42, 47, 0.8);
    border-radius: 6px;
    box-sizing: border-box;
}

#jump_app > div > :nth-child(2) {
    display: flex;
    align-items: center;
}

#jump_app > div > :last-child {
    width: 100%;
    position: absolute;
    margin: 0 auto;
    text-align: center;
    bottom: 80px;
}

.jump_gameBtn {
    display: inline-block;
    margin: 0 auto;
    font-size: 26px;
    cursor: pointer;
    color: #fff;
    background-color: #4495fb;
    border: none;
    padding: 4px 10px;
    border-radius: 4px;
    outline: none;
}

label {
    margin-left: 50px;
}

select {
    font-size: 18px;
    outline: none;
    margin-left: 30px;
    height: 34px;
    width: 150px;
}

h1 {
    padding-top: 15px;
    text-align: center;
}

#jump_restartGame {
    display: none;
}

#jump_score {
    position: absolute;
    width: 100%;
    display: none;
    text-align: center;
    z-index: 100;
    top: 30px;
    font-size: 24px;
}