.btn-file {
    position: relative;
    overflow: hidden;
}

    .btn-file input[type=file] {
        position: absolute;
        top: 0;
        right: 0;
        min-width: 100%;
        min-height: 100%;
        font-size: 100px;
        text-align: right;
        filter: alpha(opacity=0);
        opacity: 0;
        outline: none;
        background: white;
        cursor: inherit;
        display: block;
    }

.loading-spinner {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    border: 6px solid #f3f3f3;
    border-top: 6px solid #df691a;
    border-radius: 50%;
    width: 50px;
    height: 50px;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    0% {
        transform: rotate(0deg);
    }

    100% {
        transform: rotate(360deg);
    }
}