.ldnb-button {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 10px 20px;
    border-radius: 5px;
    font-size: 16px;
    font-weight: 600;
    text-decoration: none;
    transition: all 0.3s ease;
    border: none;
    cursor: pointer;
    margin: 5px;
}

.ldnb-prev, .ldnb-next {
    background-color: #3498db;
    color: white;
}

.ldnb-complete {
    background-color: #2ecc71;
    color: white;
}

.ldnb-back-to-course {
    background-color: #34495e;
    color: white;
}

.ldnb-button:hover {
    opacity: 0.9;
}

.ldnb-button i {
    margin-right: 5px;
}

.ldnb-complete.processing {
    background-color: #f39c12;
    pointer-events: none;
}

.ldnb-complete.completed {
    background-color: #27ae60;
}

.loading-spinner {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 3px solid rgba(255,255,255,0.3);
    border-radius: 50%;
    border-top: 3px solid #ffffff;
    animation: spin 1s linear infinite;
    margin-right: 10px;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}