.vault-container {
    max-width: 1200px;
    margin: 20px auto;
    border: 1px solid #243a52;
    background: #142538;
    color: #fce313;
    font-size: 16px;
    border-radius: 5px;
    box-shadow: 3px 3px 3px grey;
}

.vault-header {
    padding: 15px;
    font-size: 1.6em;
    text-align: center;
    background: #1c2f45;
    border-bottom: 1px solid #243a52;
}

.vault-body {
    display: flex;
    height: 600px;
}

/* LEFT NAV */
.vault-nav {
    width: 35%;
    background: #16283d;
    border-right: 1px solid #243a52;
    overflow-y: auto;
    padding: 15px;
}

.vault-nav ul,
.vault-nav li {
    list-style: none;
    margin: 0;
    padding: 0;
}

/* TREE STRUCTURE */
.tree ul {
    list-style: none;
    padding-left: 20px;
    overflow: hidden;
    max-height: 0;
    opacity: 0;
    transition: max-height 0.35s ease, opacity 0.25s ease;
}

.tree ul.open {
    max-height: 1000px; /* large enough for content */
    opacity: 1;
}

/* FOLDERS */
.folder {
    cursor: pointer;
    display: block;
    padding: 6px 8px;
    border-radius: 4px;
    transition: background 0.2s ease;
}

.folder:hover {
    background: #243a52;
}

/* Arrow rotation */
.folder::before {
    content: "▸ ";
    display: inline-block;
    transition: transform 0.25s ease;
}

.folder.open::before {
    transform: rotate(90deg);
}

/* FILES */
.file {
    cursor: pointer;
    display: block;
    padding: 6px 8px;
    border-radius: 4px;
    color: #a8d8ff;
    transition: background 0.2s ease;
}

.file:hover {
    background: #243a52;
}

.file.active {
    background: #2f4a66;
}

/* RIGHT CONTENT */
.vault-content {
    flex: 1;
    padding: 25px;
}

.vault-content h2 {
    margin-top: 0;
}

.file-meta {
    margin-top: 20px;
    line-height: 1.6em;
}

.download-btn {
    margin-top: 30px;
    padding: 12px 30px;
    font-size: 1em;
    font-weight: bold;
    background: #fce313;
    color: #142538;
    border: none;
    border-radius: 6px;
    cursor: pointer;
}

.download-btn:disabled {
    opacity: 0.4;
    cursor: not-allowed;
}