.panel-left {
    width: 468px;
    min-width: 180px;
    max-width: 70vw;
    background: linear-gradient(180deg, var(--left-dark-1), var(--left-dark-2));
    border: 1px solid rgba(255, 255, 255, 0.08);
}

.panel-left .section-surface {
    background: linear-gradient(180deg, rgba(255, 255, 255, 0.08), rgba(255, 255, 255, 0.05));
    border: 1px solid var(--left-border);
    color: var(--left-text);
}

.panel-left .app-bar {
    background: linear-gradient(135deg, #0f1b2d, #163052, #204472);
}

.panel-left .card-header {
    border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}

.panel-left .card-header h2,
.panel-left .card-body {
    color: var(--left-text);
}

.panel-left .badge {
    background: rgba(255, 255, 255, 0.12);
    color: white;
    border: 1px solid rgba(255, 255, 255, 0.14);
}

#leftTopics {
    height: 390px;
}

#leftExercises {
    flex: 1 1 auto;
}

.item-list {
    margin: 0;
    padding-left: 18px;
    list-style: disc;
}

.item-list li {
    padding: 2px 4px;
    margin-bottom: 0;
    border-radius: 8px;
    line-height: 1.15;
}

.topic-item,
.exercise-item {
    cursor: pointer;
    transition: background 0.15s ease, transform 0.15s ease;
}

.topic-item:hover,
.exercise-item:hover {
    background: rgba(255, 255, 255, 0.12);
    transform: translateX(2px);
}

.topic-item.selected {
    background: rgba(255, 255, 255, 0.18);
    color: #ffffff;
    font-weight: 600;
}