:root {
    --bg-color: #ffffff;
    --text-color: #1d1d1f;
    --accent-color: #0071e3;
    --secondary-bg: #f5f5f7;
    --panel-bg: rgba(255, 255, 255, 0.7);
    --border-color: rgba(0, 0, 0, 0.1);
    --font-main: 'Helvetica Neue', 'Helvetica', 'Arial', sans-serif;
    --transition: cubic-bezier(0.25, 0.1, 0.25, 1);
}

[data-theme="dark"] {
    --bg-color: #000000;
    --text-color: #f5f5f7;
    --accent-color: #0071e3;
    --secondary-bg: #1d1d1f;
    --panel-bg: rgba(29, 29, 31, 0.7);
    --border-color: rgba(255, 255, 255, 0.1);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    -webkit-font-smoothing: antialiased;
}

body {
    font-family: var(--font-main);
    background-color: var(--bg-color);
    color: var(--text-color);
    height: 100vh;
    display: flex;
    flex-direction: column;
    overflow: hidden;
    transition: background-color 0.5s var(--transition);
}

.page-title {
    position: fixed;
    top: 30px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 28px;
    font-weight: 300;
    letter-spacing: 8px;
    text-transform: uppercase;
    z-index: 100;
    opacity: 0.8;
    pointer-events: none;
}

header {
    height: 64px;
    padding: 0 32px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: var(--panel-bg);
    backdrop-filter: saturate(180%) blur(20px);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
}

.logo {
    font-weight: 600;
    font-size: 19px;
    letter-spacing: -0.5px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.logo span {
    background: var(--accent-color);
    color: white;
    width: 24px;
    height: 24px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 6px;
    font-size: 14px;
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: 12px;
}

.btn {
    height: 36px;
    padding: 0 16px;
    border-radius: 18px;
    border: none;
    font-family: var(--font-main);
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

.btn-primary {
    background-color: var(--text-color);
    color: var(--bg-color);
}

.btn-primary:hover {
    transform: scale(1.02);
    opacity: 0.9;
}

.btn-icon {
    width: 36px;
    padding: 0;
    background: transparent;
    color: var(--text-color);
    border: 1px solid var(--border-color);
}

.btn-icon:hover {
    background: var(--secondary-bg);
}

#container {
    flex: 1;
    display: flex;
    position: relative;
    background-image:
        radial-gradient(var(--border-color) 1px, transparent 1px);
    background-size: 40px 40px;
}

#sidebar {
    width: 280px;
    border-right: 1px solid var(--border-color);
    background: var(--bg-color);
    padding: 24px;
    display: flex;
    flex-direction: column;
    gap: 24px;
    transition: transform 0.4s var(--transition);
    z-index: 900;
}

#sidebar.hidden {
    transform: translateX(-100%);
    position: absolute;
}

.sidebar-section h3 {
    font-size: 12px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 12px;
    color: var(--text-color);
    opacity: 0.5;
}

.file-list {
    list-style: none;
}

.file-item {
    height: 40px;
    padding: 0 12px;
    display: flex;
    align-items: center;
    border-radius: 8px;
    cursor: pointer;
    font-size: 14px;
    transition: all 0.2s;
    margin-bottom: 4px;
}

.file-item:hover {
    background: var(--secondary-bg);
}

.file-item.active {
    background: var(--accent-color);
    color: white;
}

#main-view {
    flex: 1;
    height: 100%;
    position: relative;
}

svg#markmap {
    width: 100%;
    height: 100%;
}

/* Custom Markmap Styling */
.markmap-node {
    cursor: pointer;
}

.markmap-link {
    stroke: var(--text-color);
    stroke-opacity: 0.15;
}

/* Tooltip & UI Helpers */
.hint {
    position: absolute;
    bottom: 24px;
    right: 24px;
    background: var(--panel-bg);
    backdrop-filter: blur(10px);
    padding: 8px 16px;
    border-radius: 8px;
    font-size: 12px;
    border: 1px solid var(--border-color);
    opacity: 0.7;
}

#drop-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0, 113, 227, 0.15);
    backdrop-filter: blur(8px);
    display: none;
    z-index: 2000;
    justify-content: center;
    align-items: center;
    pointer-events: none;
}

#drop-overlay.active {
    display: flex;
    border: 4px dashed var(--accent-color);
}

.drop-content {
    text-align: center;
}

.drop-content h2 {
    font-size: 32px;
    font-weight: 300;
    color: var(--accent-color);
}