style.css

:root {
    --color-status: #4D4D4D;
    --font-size-minutes: 5rem;
    --progress: 100;
}

* {
    margin: 0;
    padding: 0;
}

body {
    align-items: center;
    background-color: #FFF;
    color: #4D4D4D;
    display: flex;
    font-family: "Roboto", "Arial", sans-serif;
    font-size: 1rem;
    font-weight: 300;
    flex-direction: column;
    justify-content: center;
    min-height: 100vh;
}

.time {
    color: var(--color-status);
    font-size: 5rem;
    font-weight: 100;
}

#minutes {
    font-size: var(--font-size-minutes);
    margin-right: .15em;
    transition: font-size 1s;
}

.circular-progress-container {
    position: fixed;
    height: 300px;
    width: 300px;
}

.progress {
    fill: none;
    stroke: var(--color-status);
    stroke-dasharray: var(--progress), 100;
    stroke-linecap: round;
    stroke-width: 1;
}

#circular-progress-bottom {
    fill: none;
    stroke: #DDD;
    stroke-dasharray: 100, 100;
    stroke-linecap: round;  
    stroke-width: .5;
}

#circular-progress-background {
    stroke: #FFF;
}

#circular-progress {
    animation: progress-color 1s linear 0s infinite alternate;
}

@keyframes progress-color {
    from { opacity: 1; }
    to { opacity: .5; }
}