:root {
    /* Color System */
    --bg-primary: #0f0f0f;
    --bg-secondary: #1a1a1a;
    --bg-tertiary: #252525;
    --surface: #2a2a2a;
    --surface-elevated: #353535;
    --border: #404040;
    --border-focus: #555555;
    
    /* Text Colors */
    --text-primary: #f0f0f0;
    --text-secondary: #b0b0b0;
    --text-muted: #808080;
    
    /* Accent Colors */
    --accent-primary: #00e5ff;
    --accent-secondary: #1976d2;
    --accent-success: #4caf50;
    --accent-warning: #ff9800;
    --accent-error: #f44336;
    
    /* Material Colors */
    --mercury: #c5c5c5;
    --water: #2196f3;
    --oil: #795548;
    --plasma: #e91e63;
    
    /* Layout */
    --header-height: 60px;
    --sidebar-width: 320px;
    --border-radius: 6px;
    --spacing-xs: 4px;
    --spacing-sm: 8px;
    --spacing-md: 16px;
    --spacing-lg: 24px;
    --spacing-xl: 32px;
}

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

body {
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    height: 100vh;
    overflow: hidden;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

.app {
    display: grid;
    grid-template-columns: 1fr var(--sidebar-width);
    grid-template-rows: var(--header-height) 1fr;
    height: 100vh;
}

/* Header */
.header {
    grid-column: 1 / -1;
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 var(--spacing-lg);
    position: relative;
    z-index: 10;
}

.header-left {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

.app-title {
    font-family: 'JetBrains Mono', monospace;
    font-size: 1.4rem;
    font-weight: 600;
    color: var(--accent-primary);
    letter-spacing: -0.02em;
}

.version {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
    color: var(--text-muted);
    background: var(--surface);
    padding: 2px 6px;
    border-radius: 3px;
}

.header-center {
    position: absolute;
    left: 50%;
    transform: translateX(-50%);
}

.physics-status {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.8rem;
}

.status-indicator {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: var(--text-muted);
    animation: pulse 2s infinite;
}

.status-indicator.active {
    background: var(--accent-success);
}

.status-text {
    color: var(--text-secondary);
}

.header-right {
    display: flex;
    gap: var(--spacing-sm);
}

/* Buttons */
.btn {
    font-family: 'Inter', sans-serif;
    font-size: 0.875rem;
    font-weight: 500;
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--border-radius);
    border: none;
    cursor: pointer;
    transition: all 0.2s ease;
    outline: none;
}

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

.btn-primary:hover {
    background: #00d4ea;
    transform: translateY(-1px);
}

.btn-secondary {
    background: var(--surface);
    color: var(--text-primary);
    border: 1px solid var(--border);
}

.btn-secondary:hover {
    background: var(--surface-elevated);
    border-color: var(--border-focus);
}

/* Main Canvas Area */
.main {
    position: relative;
    background: var(--bg-primary);
    overflow: hidden;
}

.canvas {
    width: 100%;
    height: 100%;
    display: block;
    cursor: crosshair;
}

.canvas-controls {
    position: absolute;
    top: var(--spacing-lg);
    left: var(--spacing-lg);
    z-index: 5;
}

.gravity-btn {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    background: rgba(42, 42, 42, 0.9);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border);
    color: var(--text-secondary);
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: all 0.2s ease;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.8rem;
}

.gravity-btn:hover {
    background: rgba(53, 53, 53, 0.95);
    color: var(--text-primary);
    border-color: var(--border-focus);
}

.gravity-btn.active {
    background: rgba(0, 229, 255, 0.1);
    border-color: var(--accent-primary);
    color: var(--accent-primary);
}

/* Control Panel */
.control-panel {
    background: var(--bg-secondary);
    border-left: 1px solid var(--border);
    padding: var(--spacing-lg);
    overflow-y: auto;
    height: 100%;
}

.panel-section {
    margin-bottom: var(--spacing-xl);
}

.section-title {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: var(--spacing-md);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.control-group {
    margin-bottom: var(--spacing-lg);
}

.control-label {
    display: block;
    font-family: 'Inter', sans-serif;
    font-size: 0.8rem;
    font-weight: 500;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
}

/* Material Selector */
.material-selector {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-sm);
}

.material-btn {
    background: var(--surface);
    border: 1px solid var(--border);
    color: var(--text-secondary);
    padding: var(--spacing-sm);
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: all 0.2s ease;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.material-btn:hover {
    background: var(--surface-elevated);
    border-color: var(--border-focus);
    color: var(--text-primary);
}

.material-btn.active {
    border-color: var(--accent-primary);
    background: rgba(0, 229, 255, 0.1);
    color: var(--accent-primary);
}

.material-btn[data-material="mercury"].active {
    border-color: var(--mercury);
    background: rgba(197, 197, 197, 0.1);
    color: var(--mercury);
}

.material-btn[data-material="water"].active {
    border-color: var(--water);
    background: rgba(33, 150, 243, 0.1);
    color: var(--water);
}

.material-btn[data-material="oil"].active {
    border-color: var(--oil);
    background: rgba(121, 85, 72, 0.1);
    color: var(--oil);
}

.material-btn[data-material="plasma"].active {
    border-color: var(--plasma);
    background: rgba(233, 30, 99, 0.1);
    color: var(--plasma);
}

/* Sliders */
.slider-container {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

.slider {
    flex: 1;
    -webkit-appearance: none;
    appearance: none;
    height: 4px;
    background: var(--surface);
    border-radius: 2px;
    outline: none;
    cursor: pointer;
}

.slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 16px;
    height: 16px;
    background: var(--accent-primary);
    border-radius: 50%;
    cursor: pointer;
    transition: all 0.2s ease;
}

.slider::-webkit-slider-thumb:hover {
    background: #00d4ea;
    transform: scale(1.1);
}

.slider::-moz-range-thumb {
    width: 16px;
    height: 16px;
    background: var(--accent-primary);
    border-radius: 50%;
    border: none;
    cursor: pointer;
    transition: all 0.2s ease;
}

.slider-value {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
    color: var(--text-muted);
    min-width: 45px;
    text-align: right;
}

/* Stats Grid */
.stats-grid {
    display: grid;
    gap: var(--spacing-sm);
}

.stat-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-sm);
    background: var(--surface);
    border-radius: var(--border-radius);
    border: 1px solid var(--border);
}

.stat-label {
    font-family: 'Inter', sans-serif;
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.stat-value {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--accent-primary);
}

/* Animations */
@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.5; }
}

/* Responsive Design */
@media (max-width: 1024px) {
    .app {
        grid-template-columns: 1fr;
        grid-template-rows: var(--header-height) 1fr auto;
    }
    
    .control-panel {
        position: fixed;
        bottom: 0;
        left: 0;
        right: 0;
        height: 200px;
        border-left: none;
        border-top: 1px solid var(--border);
        padding: var(--spacing-md);
    }
    
    .panel-section {
        margin-bottom: var(--spacing-md);
    }
    
    .section-title {
        font-size: 0.8rem;
        margin-bottom: var(--spacing-sm);
    }
}

/* Smooth transitions */
* {
    transition: border-color 0.2s ease, background-color 0.2s ease, color 0.2s ease;
}