ul.tree, ul.tree ul {
    list-style: none;
    margin: 0;
    padding-left: 15px;
    position: relative;
}

ul.tree ul::before {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    border-left: 1px solid #ccc;
    height: 100%;
}

ul.tree li {
    margin: 6px 0;
    padding-left: 18px;
    position: relative;
    cursor: pointer;
}

ul.tree li::before {
    content: "";
    position: absolute;
    top: 12px;
    left: 0;
    width: 12px;
    border-top: 1px solid #ccc;
}

ul.tree li:hover {
    background: #f5f5f5;
}

.nested {
    display: none;
}

.active {
    display: block;
}

.caret::before {
    content: "▶";
    margin-right: 6px;
    font-size: 10px;
}

.caret-down::before {
    transform: rotate(90deg);
}

.playing {
    background: #e3f2fd;
    font-weight: bold;
}

.play-btn {
    margin-left: 8px;
    padding: 4px 8px;
    font-size: 14px;
}

/* 📱 Mobile improvements */
@media (max-width: 768px) {
    .node-title {
        font-size: 16px;
    }

    .play-btn {
        font-size: 16px;
        padding: 6px 10px;
    }

    ul.tree li {
        padding: 12px 8px;
    }
}

/* 🎧 Sticky player */
.player-container {
    position: sticky;
    bottom: 0;
    background: white;
    padding: 10px;
    border-top: 1px solid #ccc;
}