* {
padding: 0;
margin: 0;
}

body {
background-color: rgb(60, 60, 60);
height: 100vh;
}

.container-clock {
/* 置中 */
position: absolute; 
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
background-color: transparent;
border: 3px solid lightgreen;
color: lightgreen;
width: 340px;
padding: 10px;
border-radius: 40px;
transition: 0.5s;
}

.container-clock:hover {
background-color: lightgreen;
color: black;
box-shadow: 0 0 30px lightgreen;
}

.time {
font-size: 50px;
font-weight: 600px;
text-align: center;
}

.date {
font-size: 20px;
text-align: center;
font-style: italic;
}

#period {
font-size: 20px;
}