.placeholder {
    display: inline-block;
    min-height: 1em;
    vertical-align: middle;
    cursor: wait;
    opacity: 0.5;
    animation: placeholder-glow 1.5s infinite;
}

.placeholder:not(.btn) {
    background-color: currentcolor;
}

.placeholder-fixed {
    display: inline-block;
    min-height: 1em;
    vertical-align: middle;
    cursor: wait;
    background-color: currentcolor;
    opacity: 0.5;
}

.placeholder-xs {
    min-height: 0.6em;
}

.placeholder-sm {
    min-height: 0.8em;
}

.placeholder-lg {
    min-height: 1.2em;
}

.placeholder.btn::before {
    content: "";
    display: inline-block;
}

@keyframes placeholder-glow {
    50% {
        opacity: 0.2;
    }
}