:root {
    --bg-primary: #0F172A;
    --bg-secondary: #1E293B;
    --bg-card: rgba(30, 41, 59, 0.85);
    --border-color: rgba(255, 255, 255, 0.1);
    --text-primary: #F8FAFC;
    --text-muted: #94A3B8;
    --accent-blue: #3B82F6;
    --accent-blue-hover: #2563EB;
    --accent-green: #10B981;
    --accent-orange: #F59E0B;
    --accent-purple: #8B5CF6;
    --accent-red: #EF4444;
    --shadow-card: 0 10px 25px -5px rgba(0, 0, 0, 0.3), 0 8px 10px -6px rgba(0, 0, 0, 0.3);
    --radius-lg: 16px;
    --radius-md: 12px;
    --radius-sm: 8px;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
}

body {
    background-color: var(--bg-primary);
    color: var(--text-primary);
    display: flex;
    min-height: 100vh;
}

/* Sidebar Navigation */
.sidebar {
    width: 260px;
    background: var(--bg-secondary);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    padding: 24px 16px;
    flex-shrink: 0;
}

.brand {
    display: flex;
    align-items: center;
    gap: 12px;
    padding-bottom: 24px;
    margin-bottom: 20px;
    border-bottom: 1px solid var(--border-color);
}

.brand-icon {
    font-size: 28px;
    background: linear-gradient(135deg, #3B82F6, #8B5CF6);
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 12px;
}

.brand-title {
    font-size: 18px;
    font-weight: 700;
    letter-spacing: -0.3px;
}

.brand-sub {
    font-size: 11px;
    color: var(--text-muted);
}

.nav-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 6px;
    flex: 1;
}

.nav-item a {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 16px;
    color: var(--text-muted);
    text-decoration: none;
    border-radius: var(--radius-md);
    font-weight: 600;
    font-size: 14px;
    transition: all 0.2s ease;
}

.nav-item a:hover, .nav-item.active a {
    color: var(--text-primary);
    background: rgba(59, 130, 246, 0.15);
    border: 1px solid rgba(59, 130, 246, 0.3);
}

.nav-item.active a {
    background: linear-gradient(90deg, rgba(59, 130, 246, 0.25), rgba(139, 92, 246, 0.15));
    border-color: var(--accent-blue);
}

/* Main Content Area */
.main-wrapper {
    flex: 1;
    display: flex;
    flex-direction: column;
    overflow-y: auto;
    max-height: 100vh;
}

.top-bar {
    padding: 16px 32px;
    background: rgba(30, 41, 59, 0.6);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: sticky;
    top: 0;
    z-index: 100;
}

.content-container {
    padding: 32px;
    flex: 1;
}

/* Stat Grid */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 20px;
    margin-bottom: 32px;
}

.stat-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 24px;
    box-shadow: var(--shadow-card);
    display: flex;
    align-items: center;
    gap: 18px;
    transition: transform 0.2s ease;
}

.stat-card:hover {
    transform: translateY(-3px);
}

.stat-icon-wrapper {
    width: 52px;
    height: 52px;
    border-radius: 14px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
}

.stat-val {
    font-size: 28px;
    font-weight: 800;
}

.stat-label {
    font-size: 13px;
    color: var(--text-muted);
    font-weight: 600;
}

/* Cards & Panels */
.card-panel {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 24px;
    box-shadow: var(--shadow-card);
    margin-bottom: 24px;
}

.panel-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    padding-bottom: 12px;
    border-bottom: 1px solid var(--border-color);
}

.panel-title {
    font-size: 18px;
    font-weight: 700;
    display: flex;
    align-items: center;
    gap: 8px;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 10px 18px;
    border-radius: var(--radius-md);
    font-weight: 600;
    font-size: 14px;
    cursor: pointer;
    border: none;
    text-decoration: none;
    transition: all 0.2s ease;
}

.btn-primary {
    background: linear-gradient(135deg, #3B82F6, #2563EB);
    color: #FFFFFF;
    box-shadow: 0 4px 14px rgba(37, 99, 235, 0.4);
}

.btn-primary:hover {
    background: linear-gradient(135deg, #2563EB, #1D4ED8);
    transform: translateY(-1px);
}

.btn-success {
    background: linear-gradient(135deg, #10B981, #059669);
    color: #FFFFFF;
    box-shadow: 0 4px 14px rgba(16, 185, 129, 0.4);
}

.btn-success:hover {
    background: linear-gradient(135deg, #059669, #047857);
}

.btn-secondary {
    background: rgba(255, 255, 255, 0.08);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover {
    background: rgba(255, 255, 255, 0.15);
}

.btn-danger {
    background: rgba(239, 68, 68, 0.2);
    color: #EF4444;
    border: 1px solid rgba(239, 68, 68, 0.3);
}

.btn-danger:hover {
    background: #EF4444;
    color: #FFFFFF;
}

/* Table */
.data-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 14px;
}

.data-table th, .data-table td {
    padding: 14px 16px;
    text-align: left;
    border-bottom: 1px solid var(--border-color);
}

.data-table th {
    color: var(--text-muted);
    font-weight: 600;
    text-transform: uppercase;
    font-size: 12px;
    letter-spacing: 0.5px;
}

.data-table tr:hover td {
    background: rgba(255, 255, 255, 0.02);
}

/* Badges */
.badge {
    padding: 4px 10px;
    border-radius: 20px;
    font-size: 12px;
    font-weight: 700;
    display: inline-block;
}

.badge-easy { background: rgba(16, 185, 129, 0.2); color: #10B981; }
.badge-medium { background: rgba(59, 130, 246, 0.2); color: #3B82F6; }
.badge-hard { background: rgba(245, 158, 11, 0.2); color: #F59E0B; }
.badge-expert { background: rgba(239, 68, 68, 0.2); color: #EF4444; }
.badge-master { background: rgba(139, 92, 246, 0.2); color: #8B5CF6; }

/* Forms */
.form-group {
    margin-bottom: 20px;
}

.form-label {
    display: block;
    font-size: 13px;
    font-weight: 600;
    color: var(--text-muted);
    margin-bottom: 8px;
}

.form-input, .form-select, .form-textarea {
    width: 100%;
    padding: 12px 14px;
    background: rgba(15, 23, 42, 0.6);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-size: 14px;
    outline: none;
    transition: border-color 0.2s ease;
}

.form-input:focus, .form-select:focus, .form-textarea:focus {
    border-color: var(--accent-blue);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.2);
}

/* Alert & Notifications */
.alert {
    padding: 14px 18px;
    border-radius: var(--radius-md);
    margin-bottom: 20px;
    font-size: 14px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.alert-success { background: rgba(16, 185, 129, 0.15); border: 1px solid #10B981; color: #10B981; }
.alert-danger { background: rgba(239, 68, 68, 0.15); border: 1px solid #EF4444; color: #EF4444; }

/* Visual Level Editor Canvas */
.editor-layout {
    display: grid;
    grid-template-columns: 1.15fr 1fr;
    gap: 24px;
}

.board-canvas-container {
    background: #0B1120;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 16px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 560px;
    max-height: 680px;
    position: relative;
    overflow: auto;
}

#editorCanvas {
    background: #111827;
    border-radius: 12px;
    border: 1px solid var(--border-color);
    cursor: crosshair;
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.5);
}

/* Tabs */
.tab-bar {
    display: flex;
    gap: 8px;
    border-bottom: 1px solid var(--border-color);
    margin-bottom: 20px;
    padding-bottom: 8px;
}

.tab-btn {
    padding: 8px 16px;
    background: transparent;
    border: 1px solid transparent;
    border-radius: var(--radius-md);
    color: var(--text-muted);
    font-weight: 700;
    font-size: 13px;
    cursor: pointer;
    transition: all 0.2s ease;
}

.tab-btn:hover {
    color: var(--text-primary);
    background: rgba(255, 255, 255, 0.05);
}

.tab-btn.active {
    color: #FFFFFF;
    background: var(--accent-blue);
    border-color: var(--accent-blue);
}

.tab-pane {
    display: none;
}

.tab-pane.active {
    display: block;
}

/* JSON Code Editor */
.code-editor-container {
    position: relative;
}

.json-textarea {
    width: 100%;
    height: 380px;
    background: #090D16;
    color: #38BDF8;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 14px;
    font-family: 'Consolas', 'Courier New', monospace;
    font-size: 12px;
    line-height: 1.5;
    outline: none;
    resize: vertical;
    white-space: pre;
}

.json-textarea:focus {
    border-color: var(--accent-blue);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.2);
}

.color-swatch-list {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
    margin-top: 8px;
}

.color-swatch {
    width: 32px;
    height: 32px;
    border-radius: 8px;
    cursor: pointer;
    border: 2px solid transparent;
    transition: transform 0.15s ease;
}

.color-swatch.active {
    border-color: #FFFFFF;
    transform: scale(1.15);
}