style.css

@import url('https://fonts.googleapis.com/css2?family=Karla:wght@300;400;500;600;700&display=swap');

* {
    box-sizing: border-box;
}

:root {
    --primary-color: #FFFFFF;
    --secondary-color: #303F9F;
    --text-color: #607D8B;
}

body.dark {
    --primary-color: #303F9F;
    --secondary-color: #607D8B;
    --text-color: #FFFFFF;
}

body {
    position: relative;
    font-family: 'Karla', sans-serif;
    display: flex;
    flex-direction: column;
    align-items: center;
    overflow: hidden;
    margin: 0;
    height: 100vh;
    background-color: var(--primary-color);
    transition: all 0.3s ease-in;
}

h1 {
    color: var(--text-color);
    font-weight: 300;
    font-size: 40px;
    text-transform: uppercase;
    margin-top: 40px;
}

.clock {
    margin-top: 30px;
    max-width: 100%;
    max-height: 100%;
    width: 250px;
    height: 250px;
    background-color: var(--primary-color);
    box-shadow: 0 15px 15px rgba(0, 0, 0, 0.35);
    position: relative;
    border: 5px solid rgb(243, 243, 243);
    border-radius: 50%;
    overflow: hidden;
    user-select: none;
}

.clock::before {
    content: '';
    background-image: url('Image/lightClock.jpg');
    background-position: center center;
    background-size: cover;
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 1;
    transition: background-image 0.3s linear;
}

.needle {
    width: 3px;
    height: 80px;
    border-radius: 10px;
    background-color: var(--secondary-color);
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -100%) rotate(0deg);
    transform-origin: bottom center;
    z-index: 2;
}

.hour {
    width: 5px;
    height: 65px;
}

.second {
    height: 85px;
    background-color: red;
}

.center-point {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 13px;
    height: 13px;
    background-color: var(--secondary-color);
    border-radius: 50%;
    border: 3px solid red;
    z-index: 3;
}

button {
    position: absolute;
    bottom: 30px;
    left: 50%;
    transform: translateX(-50%);
    border: 1px solid var(--secondary-color);
    outline: 0;
    background-color: transparent;
    padding: 8px 15px;
    border-radius: 5px;
    font-family: inherit;
    text-transform: uppercase;
    font-size: 14px;
    font-weight: 500;
    color: var(--secondary-color);
    cursor: pointer;
    user-select: none;
}

button:active {
    transform: scale(0.98) translateX(-50%);
}

body.dark button {
    border: 2px solid var(--text-color);
    color: var(--text-color);
}