progress-linear.css

.matter-progress-linear {
    --matter-helper-theme: var(--matter-theme-rgb, var(--matter-primary-rgb, 33, 150, 243));
    -webkit-appearance: none;
    -moz-appearance: none;
    appearance: none;
    border: none;
    width: 160px;
    height: 4px;
    vertical-align: middle;
    color: rgb(var(--matter-helper-theme));
    background-color: rgba(var(--matter-helper-theme), 0.12);
}

.matter-progress-linear::-webkit-progress-bar {
    background-color: transparent;
}

/* Determinate */
.matter-progress-linear::-webkit-progress-value {
    background-color: currentColor;
    transition: all 0.2s;
}

.matter-progress-linear::-moz-progress-bar {
    background-color: currentColor;
    transition: all 0.2s;
}

.matter-progress-linear::-ms-fill {
    border: none;
    background-color: currentColor;
    transition: all 0.2s;
}

/* Indeterminate */
.matter-progress-linear:indeterminate {
    background-size: 200% 100%;
    background-image:
        linear-gradient(to right, currentColor 16%, transparent 16%),
        linear-gradient(to right, currentColor 16%, transparent 16%),
        linear-gradient(to right, currentColor 25%, transparent 25%);
    animation: matter-progress-linear 1.8s infinite linear;
}

.matter-progress-linear:indeterminate::-webkit-progress-value {
    background-color: transparent;
}

.matter-progress-linear:indeterminate::-moz-progress-bar {
    background-color: transparent;
}

.matter-progress-linear:indeterminate::-ms-fill {
    animation-name: none;
}

@keyframes matter-progress-linear {
    0% {
        background-position: 32% 0, 32% 0, 50% 0;
    }
    2% {
        background-position: 32% 0, 32% 0, 50% 0;
    }
    21% {
        background-position: 32% 0, -18% 0, 0 0;
    }
    42% {
        background-position: 32% 0, -68% 0, -27% 0;
    }
    50% {
        background-position: 32% 0, -93% 0, -46% 0;
    }
    56% {
        background-position: 32% 0, -118% 0, -68% 0;
    }
    66% {
        background-position: -11% 0, -200% 0, -100% 0;
    }
    71% {
        background-position: -32% 0, -200% 0, -100% 0;
    }
    79% {
        background-position: -54% 0, -242% 0, -100% 0;
    }
    86% {
        background-position: -68% 0, -268% 0, -100% 0;
    }
    100% {
        background-position: -100% 0, -300% 0, -100% 0;
    }
}