.lesson-nav {
    margin-top: 32px;
    padding: 24px;
    background: var(--bg-card, #fff);
    border: 1px solid var(--border);
    border-radius: 16px;
    box-shadow: 0 2px 8px rgba(11,31,58,.06);
}
.lesson-nav-progress {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 20px;
}
.lesson-nav-counter {
    font-size: 14px;
    font-weight: 700;
    color: var(--teal);
    white-space: nowrap;
}
.lesson-nav-bar {
    flex: 1;
    height: 6px;
    background: var(--border-soft);
    border-radius: 3px;
    overflow: hidden;
}
.lesson-nav-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--teal), var(--teal-light));
    border-radius: 3px;
    transition: width .3s ease;
}
.lesson-nav-buttons {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 12px;
}
.lesson-nav-btn {
    display: flex;
    flex-direction: column;
    gap: 4px;
    padding: 16px;
    border-radius: 12px;
    border: 1.5px solid var(--border);
    text-decoration: none;
    transition: all .15s;
}
.lesson-nav-btn:hover {
    border-color: var(--teal);
    background: var(--teal-bg);
    transform: translateY(-1px);
}
.lesson-nav-prev { text-align: start }
.lesson-nav-next { text-align: end }
.lesson-nav-label {
    font-size: 12px;
    font-weight: 700;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: .05em;
}
.lesson-nav-title {
    font-size: 15px;
    font-weight: 700;
    color: var(--navy);
    line-height: 1.4;
}
.lesson-nav-disabled {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 16px;
    border-radius: 12px;
    border: 1.5px dashed var(--border-soft);
    opacity: .5;
}
.lesson-nav-disabled .lesson-nav-label {
    font-size: 13px;
    color: var(--text-muted);
}
@media (max-width: 768px) {
    .lesson-nav { padding: 20px; }
    .lesson-nav-btn { padding: 14px; }
    .lesson-nav-title { font-size: 14px; }
}

@media (max-width: 640px) {
    .lesson-nav { padding: 16px }
    .lesson-nav-buttons { grid-template-columns: 1fr; gap: 8px }
    .lesson-nav-prev, .lesson-nav-next { text-align: start }
    .lesson-nav-title { font-size: 14px }
}