:root {
    --bg-primary: #0f1419;
    --bg-secondary: #1a1f2e;
    --bg-tertiary: #242b3d;
    --text-primary: #e8eaed;
    --text-secondary: #b8bbc2;
    --text-muted: #8a8d95;
    --accent-primary: #00d4ff;
    --accent-secondary: #7c3aed;
    --accent-tertiary: #10b981;
    --accent-danger: #ef4444;
    --border-color: #374151;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.5);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
}

.container {
    max-width: 1600px;
    margin: 0 auto;
    padding: 20px;
}

/* Header */
header {
    text-align: center;
    padding: 30px 20px;
    background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-tertiary) 100%);
    border-radius: 12px;
    margin-bottom: 30px;
    box-shadow: var(--shadow-md);
}

header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--accent-primary) 0%, var(--accent-secondary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 10px;
}

.subtitle {
    font-size: 1.1rem;
    color: var(--text-secondary);
    font-weight: 400;
}

/* Equation Section */
.equation-section {
    background: var(--bg-secondary);
    padding: 20px;
    border-radius: 12px;
    margin-bottom: 30px;
    box-shadow: var(--shadow-sm);
    text-align: center;
}

.equation p:first-child {
    font-size: 1rem;
    color: var(--text-secondary);
    margin-bottom: 10px;
}

.math-formula {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--accent-primary);
    font-family: 'Times New Roman', serif;
    letter-spacing: 1px;
}

/* Visualization Grid */
.visualization-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(450px, 1fr));
    gap: 20px;
    margin-bottom: 30px;
}

.viz-panel {
    background: var(--bg-secondary);
    border-radius: 12px;
    padding: 20px;
    box-shadow: var(--shadow-md);
    position: relative;
}

.viz-panel h3 {
    font-size: 1.1rem;
    color: var(--text-primary);
    margin-bottom: 15px;
    font-weight: 600;
}

.viz-panel canvas {
    width: 100%;
    height: 300px;
    background: var(--bg-tertiary);
    border-radius: 8px;
    border: 1px solid var(--border-color);
}

.panel-info {
    display: flex;
    justify-content: space-between;
    margin-top: 10px;
    font-size: 0.85rem;
    color: var(--text-muted);
}

/* Statistics Section */
.stats-section {
    background: var(--bg-secondary);
    border-radius: 12px;
    padding: 20px;
    margin-bottom: 30px;
    box-shadow: var(--shadow-sm);
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: 15px;
}

.stat-item {
    display: flex;
    flex-direction: column;
    padding: 12px;
    background: var(--bg-tertiary);
    border-radius: 8px;
    border-left: 3px solid var(--accent-primary);
}

.stat-label {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: 5px;
}

.stat-value {
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--accent-primary);
    font-family: 'Courier New', monospace;
}

/* Controls Section */
.controls-section {
    background: var(--bg-secondary);
    border-radius: 12px;
    padding: 25px;
    margin-bottom: 30px;
    box-shadow: var(--shadow-md);
}

.controls-wrapper {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 25px;
    margin-bottom: 25px;
}

.control-group {
    background: var(--bg-tertiary);
    padding: 20px;
    border-radius: 10px;
    border: 1px solid var(--border-color);
}

.control-group h3 {
    font-size: 1rem;
    color: var(--text-primary);
    margin-bottom: 15px;
    font-weight: 600;
    border-bottom: 2px solid var(--accent-primary);
    padding-bottom: 8px;
}

.control-item {
    margin-bottom: 15px;
}

.control-item label {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 8px;
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.value-display {
    font-family: 'Courier New', monospace;
    color: var(--accent-primary);
    font-weight: 600;
    padding: 2px 8px;
    background: var(--bg-secondary);
    border-radius: 4px;
    font-size: 0.85rem;
}

.control-item input[type="range"] {
    width: 100%;
    height: 6px;
    border-radius: 3px;
    background: var(--bg-secondary);
    outline: none;
    -webkit-appearance: none;
    appearance: none;
}

.control-item input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 18px;
    height: 18px;
    border-radius: 50%;
    background: var(--accent-primary);
    cursor: pointer;
    transition: all 0.2s;
}

.control-item input[type="range"]::-webkit-slider-thumb:hover {
    transform: scale(1.2);
    background: var(--accent-secondary);
}

.control-item input[type="range"]::-moz-range-thumb {
    width: 18px;
    height: 18px;
    border-radius: 50%;
    background: var(--accent-primary);
    cursor: pointer;
    border: none;
    transition: all 0.2s;
}

.control-item input[type="range"]::-moz-range-thumb:hover {
    transform: scale(1.2);
    background: var(--accent-secondary);
}

/* Presets */
.presets-group {
    grid-column: 1 / -1;
}

.preset-buttons {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.preset-btn {
    padding: 10px 20px;
    background: linear-gradient(135deg, var(--accent-primary) 0%, var(--accent-secondary) 100%);
    color: white;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 0.9rem;
    font-weight: 600;
    transition: all 0.3s;
    box-shadow: var(--shadow-sm);
}

.preset-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.preset-btn:active {
    transform: translateY(0);
}

/* Action Buttons */
.action-buttons {
    display: flex;
    flex-wrap: wrap;
    gap: 15px;
    margin-bottom: 25px;
}

.btn {
    padding: 12px 30px;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 600;
    transition: all 0.3s;
    box-shadow: var(--shadow-sm);
}

.btn-primary {
    background: linear-gradient(135deg, var(--accent-primary) 0%, var(--accent-secondary) 100%);
    color: white;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

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

.btn-secondary:hover {
    background: var(--bg-secondary);
    transform: translateY(-2px);
}

/* Visualization Options */
.viz-options {
    grid-column: 1 / -1;
}

.checkbox-group {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 12px;
}

.checkbox-item {
    display: flex;
    align-items: center;
    cursor: pointer;
    padding: 8px;
    border-radius: 6px;
    transition: background 0.2s;
}

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

.checkbox-item input[type="checkbox"] {
    width: 18px;
    height: 18px;
    margin-right: 10px;
    cursor: pointer;
    accent-color: var(--accent-primary);
}

.checkbox-item span {
    font-size: 0.9rem;
    color: var(--text-secondary);
}

/* Educational Content */
.education-section {
    margin-top: 30px;
}

.education-block {
    background: var(--bg-secondary);
    border-radius: 12px;
    margin-bottom: 20px;
    box-shadow: var(--shadow-sm);
    overflow: hidden;
}

.education-block summary {
    padding: 20px;
    cursor: pointer;
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-primary);
    background: var(--bg-tertiary);
    user-select: none;
    transition: all 0.3s;
}

.education-block summary:hover {
    background: linear-gradient(135deg, var(--bg-tertiary) 0%, var(--bg-secondary) 100%);
}

.education-block summary::-webkit-details-marker {
    display: none;
}

.education-block summary::before {
    content: '▶';
    display: inline-block;
    margin-right: 10px;
    transition: transform 0.3s;
}

.education-block[open] summary::before {
    transform: rotate(90deg);
}

.education-content {
    padding: 20px;
    border-top: 1px solid var(--border-color);
}

.education-content h4 {
    font-size: 1rem;
    color: var(--accent-primary);
    margin: 15px 0 10px 0;
    font-weight: 600;
}

.education-content h4:first-child {
    margin-top: 0;
}

.education-content p {
    font-size: 0.95rem;
    color: var(--text-secondary);
    margin-bottom: 12px;
    line-height: 1.7;
}

.education-content ul {
    list-style: none;
    padding-left: 0;
}

.education-content li {
    font-size: 0.95rem;
    color: var(--text-secondary);
    margin-bottom: 10px;
    padding-left: 25px;
    position: relative;
}

.education-content li::before {
    content: '▸';
    position: absolute;
    left: 0;
    color: var(--accent-primary);
    font-weight: bold;
}

/* Footer */
footer {
    text-align: center;
    padding: 20px;
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-top: 40px;
}

/* Responsive Design */
@media (max-width: 1200px) {
    .visualization-grid {
        grid-template-columns: repeat(auto-fit, minmax(400px, 1fr));
    }
}

@media (max-width: 768px) {
    .container {
        padding: 15px;
    }

    header h1 {
        font-size: 2rem;
    }

    .subtitle {
        font-size: 1rem;
    }

    .visualization-grid {
        grid-template-columns: 1fr;
    }

    .viz-panel canvas {
        height: 250px;
    }

    .stats-grid {
        grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    }

    .controls-wrapper {
        grid-template-columns: 1fr;
    }

    .action-buttons {
        flex-direction: column;
    }

    .btn {
        width: 100%;
    }

    .preset-buttons {
        flex-direction: column;
    }

    .preset-btn {
        width: 100%;
    }
}

@media (max-width: 480px) {
    header h1 {
        font-size: 1.5rem;
    }

    .math-formula {
        font-size: 1.2rem;
    }

    .viz-panel canvas {
        height: 200px;
    }

    .stats-grid {
        grid-template-columns: 1fr;
    }
}