:root {
    --time: 0.3s;
}
body {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    overflow: hidden;
    height: 100vh;
    margin: 0;
    background-color: rgb(40, 44, 52);
    color: white;
}
div,
h1 {
    box-shadow: none;
}
button {
    margin: 10px;
    padding: 0px 5px;
    font-size: 18px;
}
button:hover {
    padding: 10px 5px;
    transition: 0.4s;
    background-color: black;
    cursor: help;
    color: white;
}
.stop:hover {
    padding: 10px 5px;
    transition: 0.4s;
    background-color: red;
    cursor: no-drop;
    color: white;
}
.container {
    position: relative;
    overflow: hidden;
    width: 100px;
    height: 50px;
    margin-top: 20px;
}
.num {
    position: absolute;
    top: 50%;
    left: 50%;
    transition: all var(--time);
    font-size: 30px;
}
.now {
    position: absolute;
    top: 50%;
    left: 50%;
    opacity: 1;
    transform: translate(-50%, -50%);
    font-size: 30px;
}
.num.bottom {
    opacity: 0;
    transform: translate(-50%, 100%);
}
.num.in {
    opacity: 1;
    transform: translate(-50%, -50%);
}
.num.top {
    opacity: 0;
    transform: translate(-50%, -200%);
}