body {
    background-color: #0a0c10;
    color: #fff;
    font-family: system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
}
.sidebar {
    background-color: #111217;
    border-right: 1px solid #2a2c35;
    height: calc(100vh - 56px);
    position: sticky;
    top: 56px;
    overflow-y: auto;
    transition: transform 0.3s ease;
    z-index: 1050;
}
@media (max-width: 991.98px) {
    .sidebar {
        position: fixed;
        top: 56px;
        left: 0;
        width: 280px;
        transform: translateX(-100%);
        box-shadow: 2px 0 10px rgba(0,0,0,0.5);
    }
    .sidebar.open {
        transform: translateX(0);
    }
    .sidebar-header {
        display: flex;
        justify-content: space-between;
        align-items: center;
        padding: 1rem;
        border-bottom: 1px solid #2a2c35;
    }
}
@media (min-width: 992px) {
    .sidebar-header {
        display: none;
    }
}
.accordion-button:not(.collapsed) {
    background-color: #1e1e2f;
    color: #0dcaf0;
}
.accordion-button {
    background-color: #212529;
    color: white;
}
.accordion-button::after {
    filter: brightness(0) invert(1);
}
.accordion-item {
    background-color: transparent;
    border: none;
}
.list-group-item {
    background-color: transparent !important;
    border-color: #2a2c35 !important;
}
.list-group-item a {
    color: #fff;
    text-decoration: none;
    display: flex;
    align-items: center;
    padding: 8px 0;
    cursor: pointer;
}
.list-group-item a:hover {
    color: #0dcaf0;
    padding-left: 5px;
}
.leccion-contenido {
    background: #1e1e2f;
    padding: 1.5rem;
    border-radius: 16px;
    margin-bottom: 1.5rem;
}
.navegacion-leccion {
    margin-top: 2rem;
    display: flex;
    justify-content: space-between;
}
.navegacion-leccion .btn {
    padding: 8px 24px;
}
.btn-outline-info:hover {
    background-color: #0dcaf0;
    color: #000;
}