:root {
    --opacity: 0.6;
    --radius: 0.2;
    --red-limit: 80%;
    --yellow-limit: 60%;
}

.level-monitor {
    width: 50px;
    height: 300px;
    background-image: linear-gradient(
        /* Red */
        rgba(234, 68, 87, var(--opacity)) 0% calc(100% - var(--red-limit)),
        /* Yellow */
        rgba(255, 205, 76, var(--opacity)) calc(100% - var(--red-limit)) calc(100% - var(--yellow-limit)),
        /* Green */
        rgba(151, 190, 97, var(--opacity)) calc(100% - var(--yellow-limit)) 100%
    );
    position: relative;
    border-radius: var(--radius);
}

.indicator {
    width: 80%;
    background-color: rgba(0, 0, 0, 0.3);
    background-attachment: fixed;
    position: absolute;
    bottom: 0;
    left: 10%;
    border-radius: var(--radius);
}

.percent {
    width: 50px;
    font-family: Verdana, Geneva, Tahoma, sans-serif;
    font-size: 18px;
    text-align: center;
    padding: 5px 0;
}