* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
:root {
    --bg-color: #000005;
    --greeting-color: #fff;
    --contact-color: #DEDFE3;
}
body {
    background-color: var(--bg-color);
    transition: all 0.8s;
}

.greeting {
    height: 100vh;
    width: 100vw;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    flex-direction: column;
    font-family: 'Montserrat', 'Helvetica Neue', sans-serif;
    color: var(--greeting-color);
    text-align: center;
}
.greeting a {
    margin-top: 5px;
    font-style: italic;
    font-size: 1.2rem;
    color: var(--contact-color);
    text-decoration: none;
}
.themeToggle {
    position: absolute;
    top: 25px;
    right: 25px;
}
#sun,
#moon {
    cursor: pointer;
    font-size: 30px;
}
#sun {
    display: block;
    color: #fffff9;
}
#moon {
    display: none;
    color: #262930;
}
/* Khi không có class dark-mode */
body:not(.dark-mode) {
    --bg-color: #fffff9;
    --greeting-color: #262930;
    --contact-color: #656973;
}
body:not(.dark-mode) #sun {
    display: none;
}
body:not(.dark-mode) #moon {
    display: block;
}