:root {
    --primary: #3b82f6;
    --primary-dark: #2563eb;
    --secondary: #64748b;
    --success: #1094b9;
    --danger: #ef4444;
    --warning: #f59e0b;
    --background: #0f172a;
    --surface: #1e293b;
    --surface-light: #334155;
    --text: #f1f5f9;
    --text-muted: #94a3b8;
    --border: #475569;
    --muted: #64748b;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background-color: var(--background);
    color: var(--text);
    height: 100vh;
    overflow: hidden;
}

.container {
    display: flex;
    height: 100vh;
}

/* Sidebar */
.sidebar {
    width: 320px;
    background-color: var(--surface);
    border-right: 1px solid var(--border);
    overflow-y: auto;
    display: flex;
    flex-direction: column;
}

.sidebar-section {
    padding: 16px;
    border-bottom: 1px solid var(--border);
}

.section-header {
    user-select: none;
    padding: 0 -16px;
}

.section-toggle {
    font-size: 18px;
    font-weight: bold;
    color: var(--text-muted);
    transition: transform 0.2s ease;
}

.section-header.collapsed .section-toggle {
    transform: rotate(-90deg);
}

.section-content {
    transition: max-height 0.3s ease, opacity 0.3s ease;
    max-height: 1000px;
    opacity: 1;
    overflow: hidden;
}

.section-content.collapsed {
    max-height: 0;
    opacity: 0;
}

.sidebar-section h2 {
    font-size: 14px;
    font-weight: 600;
    text-transform: uppercase;
    color: var(--text-muted);
    margin-bottom: 12px;
    letter-spacing: 0.5px;
}

.sidebar-section:last-child {
    border-bottom: none;
    margin-top: auto;
}

/* Class Manager */
.class-manager {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.class-input-group {
    display: flex;
    gap: 6px;
}

.class-input-group input {
    flex: 1;
    padding: 8px 10px;
    background-color: var(--surface-light);
    border: 1px solid var(--border);
    border-radius: 6px;
    color: var(--text);
    font-size: 13px;
}

.class-input-group input::placeholder {
    color: var(--muted);
}

.class-input-group input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 2px rgba(59, 130, 246, 0.1);
}

.class-list {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.class-item {
    padding: 8px 10px;
    background-color: var(--surface-light);
    border: 1px solid var(--border);
    border-radius: 6px;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 13px;
    transition: all 0.2s ease;
}

.class-item:hover {
    background-color: rgba(59, 130, 246, 0.1);
    border-color: var(--primary);
}

.class-item.active {
    background-color: var(--primary);
    border-color: var(--primary);
    font-weight: 500;
}

.class-item-actions {
    display: flex;
    gap: 4px;
}

.class-item button {
    background: none;
    border: none;
    color: var(--text);
    cursor: pointer;
    padding: 2px 4px;
    font-size: 12px;
    opacity: 0.7;
    transition: opacity 0.2s;
}

.class-item button:hover {
    opacity: 1;
}

/* Buttons */
button {
    padding: 8px 12px;
    background-color: var(--primary);
    color: white;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    font-size: 13px;
    font-weight: 500;
    transition: all 0.2s ease;
}

button:hover {
    background-color: var(--primary-dark);
}

#colorPickerBtn {
    padding: 0;
    background-color: #ef4444;
    border: 2px solid var(--border) !important;
}

#colorPickerBtn:hover {
    background-color: #ef4444;
    border-color: var(--primary) !important;
}

.tool-btn:hover {
    background-color: var(--surface-light);
}

button:active {
    transform: scale(0.98);
}

.secondary-btn {
    background-color: var(--secondary);
}

.secondary-btn:hover {
    background-color: var(--muted);
}

.primary-btn {
    width: 100%;
    background-color: var(--success);
    font-weight: 600;
    padding: 10px;
}

.primary-btn:hover {
    background-color: #059669;
}

/* Student Manager */
.student-manager {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.student-input-group {
    display: flex;
    gap: 6px;
}

.student-input-group input {
    flex: 1;
    padding: 8px 10px;
    background-color: var(--surface-light);
    border: 1px solid var(--border);
    border-radius: 6px;
    color: var(--text);
    font-size: 13px;
}

.student-input-group input:focus {
    outline: none;
    border-color: var(--primary);
}

.student-list {
    display: flex;
    flex-direction: column;
    gap: 6px;
    max-height: 200px;
    overflow-y: auto;
}

.student-item {
    padding: 8px 10px;
    background-color: var(--surface-light);
    border: 1px solid var(--border);
    border-radius: 6px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 13px;
}

.student-item button {
    background: none;
    border: none;
    color: var(--danger);
    cursor: pointer;
    padding: 2px 6px;
    font-size: 12px;
}

/* Tools */
.tools-group {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 6px;
}

.tool-btn {
    padding: 8px;
    font-size: 12px;
    background-color: var(--surface-light);
    color: var(--text);
    border: 2px solid var(--border);
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.2s ease;
    position: relative;
}

.tool-btn:hover {
    border-color: var(--primary);
}

.tool-btn:hover::after {
    content: attr(title);
    position: absolute;
    bottom: -28px;
    left: 50%;
    transform: translateX(-50%);
    background-color: rgba(0, 0, 0, 0.9);
    color: white;
    padding: 4px 8px;
    border-radius: 4px;
    font-size: 11px;
    white-space: nowrap;
    pointer-events: none;
    z-index: 1000;
    opacity: 1;
    animation: fadeIn 0.1s ease;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

.tool-btn.active {
    background-color: var(--primary);
    border-color: var(--primary);
    color: white;
    font-weight: 600;
}

/* Constraint Type Buttons */
.constraint-buttons {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 6px;
    margin-bottom: 10px;
}

.constraint-type-btn {
    padding: 8px;
    font-size: 12px;
    background-color: var(--surface-light);
    color: var(--text);
    border: 2px solid var(--border);
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.2s ease;
}

.constraint-type-btn:hover {
    border-color: var(--primary);
}

.constraint-type-btn.active {
    background-color: var(--primary);
    border-color: var(--primary);
    color: white;
    font-weight: 600;
}

/* Settings */
.sidebar-section label {
    display: block;
    margin-bottom: 10px;
    font-size: 13px;
    display: flex;
    align-items: center;
    gap: 8px;
}

.sidebar-section input[type="number"],
.sidebar-section input[type="checkbox"] {
    padding: 6px 8px;
    background-color: var(--surface-light);
    border: 1px solid var(--border);
    border-radius: 4px;
    color: var(--text);
    font-size: 13px;
}

.sidebar-section input[type="checkbox"] {
    width: 18px;
    height: 18px;
    cursor: pointer;
}

.sidebar-section input[type="number"] {
    width: 60px;
}

/* Constraints */
.constraints-list {
    display: flex;
    flex-direction: column;
    gap: 6px;
    max-height: 200px;
    overflow-y: auto;
}

.constraint-item {
    padding: 8px 10px;
    background-color: var(--surface-light);
    border: 1px solid var(--border);
    border-radius: 6px;
    font-size: 12px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.constraint-item button {
    background: none;
    border: none;
    color: var(--danger);
    cursor: pointer;
    padding: 2px 6px;
    font-size: 11px;
}

.add-constraint {
    padding: 8px 10px;
    background-color: var(--surface-light);
    border: 1px dashed var(--border);
    border-radius: 6px;
    cursor: pointer;
    text-align: center;
    font-size: 13px;
    color: var(--text-muted);
    transition: all 0.2s ease;
}

.add-constraint:hover {
    border-color: var(--primary);
    color: var(--primary);
}

/* Seating Plan */
.seating-plan {
    display: flex;
    flex-direction: column;
    gap: 6px;
    max-height: 300px;
    overflow-y: auto;
    font-size: 12px;
}

.seating-table {
    padding: 8px;
    background-color: var(--surface-light);
    border: 1px solid var(--border);
    border-radius: 6px;
}

.seating-table-title {
    font-weight: 600;
    color: var(--primary);
    margin-bottom: 4px;
}

.seating-table-students {
    color: var(--text-muted);
    padding-left: 8px;
    word-wrap: break-word;
    overflow-wrap: break-word;
    word-break: break-word;
    white-space: normal;
}

/* Main Content */
.main-content {
    flex: 1;
    overflow: hidden;
    background-color: #ffffff;
    position: relative;
}

.canvas-controls {
    position: absolute;
    top: 10px;
    right: 10px;
    z-index: 10;
}

.export-btn {
    padding: 8px 12px;
    background-color: var(--success);
    color: rgb(255, 255, 255);
    border: none;
    border-radius: 6px;
    cursor: pointer;
    font-size: 13px;
    font-weight: 500;
    transition: all 0.2s ease;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15);
}

.export-btn:hover {
    background-color: #0f0596;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

canvas {
    display: block;
    width: 100%;
    height: 100%;
    background-color: #ffffff;
    cursor: crosshair;
}

canvas.select-cursor {
    cursor: pointer;
}

/* Seating Student Drag Styling */
.seating-student {
    transition: opacity 0.2s;
}

.seating-student:hover {
    opacity: 0.8;
    background: var(--surface) !important;
}

.seating-student[draggable="true"] {
    user-select: none;
}

.lock-btn:hover {
    color: var(--text) !important;
}

/* Scrollbar */
::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-track {
    background: transparent;
}

::-webkit-scrollbar-thumb {
    background: var(--border);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--surface-light);
}

/* Responsive */
@media (max-width: 1024px) {
    .sidebar {
        width: 280px;
    }
}

@media (max-width: 768px) {
    .container {
        flex-direction: column;
    }

    .sidebar {
        width: 100%;
        height: auto;
        max-height: 30vh;
        border-right: none;
        border-bottom: 1px solid var(--border);
    }

    .main-content {
        height: 70vh;
    }
}