/* Reset và Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary-color: #2563eb;
    --secondary-color: #0ea5e9;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --danger-color: #ef4444;
    --dark: #1e293b;
    --light: #f8fafc;
    --gray: #64748b;
    --border: #e2e8f0;
    --shadow: rgba(0, 0, 0, 0.1);
}

body {
    font-family: 'Inter', sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: var(--dark);
    line-height: 1.6;
    min-height: 100vh;
}

.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
header {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    padding: 2rem 0;
    box-shadow: 0 4px 6px var(--shadow);
    margin-bottom: 2rem;
}

header h1 {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
    display: flex;
    align-items: center;
    gap: 1rem;
}

header .subtitle {
    font-size: 1.1rem;
    color: var(--gray);
    font-weight: 300;
}

/* Grid Layout */
.grid-layout {
    display: grid;
    grid-template-columns: 350px 1fr;
    gap: 2rem;
    margin-bottom: 2rem;
}

/* Control Panel */
.control-panel {
    background: white;
    border-radius: 16px;
    padding: 2rem;
    box-shadow: 0 10px 30px var(--shadow);
    height: fit-content;
    position: sticky;
    top: 2rem;
}

.control-panel h2 {
    font-size: 1.5rem;
    color: var(--dark);
    margin-bottom: 1.5rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.control-group {
    margin-bottom: 1.5rem;
}

.control-group label {
    display: block;
    font-weight: 500;
    color: var(--dark);
    margin-bottom: 0.5rem;
    font-size: 0.95rem;
}

.control-group label i {
    color: var(--primary-color);
    margin-right: 0.3rem;
}

.control-group span {
    color: var(--primary-color);
    font-weight: 600;
}

input[type="range"] {
    width: 100%;
    height: 6px;
    border-radius: 5px;
    background: var(--border);
    outline: none;
    -webkit-appearance: none;
}

input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--primary-color);
    cursor: pointer;
    transition: all 0.3s ease;
}

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

input[type="range"]::-moz-range-thumb {
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--primary-color);
    cursor: pointer;
    border: none;
    transition: all 0.3s ease;
}

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

/* Buttons */
.control-buttons {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 0.5rem;
    margin: 2rem 0;
}

.btn {
    padding: 0.75rem 1rem;
    border: none;
    border-radius: 8px;
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    color: white;
}

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

.btn-primary:hover:not(:disabled) {
    background: #059669;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(16, 185, 129, 0.4);
}

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

.btn-warning:hover:not(:disabled) {
    background: #d97706;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(245, 158, 11, 0.4);
}

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

.btn-danger:hover:not(:disabled) {
    background: #dc2626;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(239, 68, 68, 0.4);
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* Physics Info */
.physics-info {
    background: linear-gradient(135deg, #667eea15 0%, #764ba215 100%);
    border-radius: 12px;
    padding: 1.5rem;
    margin-top: 2rem;
}

.physics-info h3 {
    font-size: 1.1rem;
    color: var(--dark);
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.info-item {
    display: flex;
    justify-content: space-between;
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--border);
}

.info-item:last-child {
    border-bottom: none;
}

.info-item span {
    color: var(--gray);
    font-size: 0.9rem;
}

.info-item strong {
    color: var(--primary-color);
    font-weight: 600;
}

/* Simulation Area */
.simulation-area {
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

.canvas-container {
    background: white;
    border-radius: 16px;
    padding: 2rem;
    box-shadow: 0 10px 30px var(--shadow);
    position: relative;
}

#pendulumCanvas {
    width: 100%;
    height: 500px;
    display: block;
    border-radius: 8px;
    background: linear-gradient(to bottom, #e0f2fe 0%, #f8fafc 100%);
}

.time-display {
    position: absolute;
    top: 2.5rem;
    right: 2.5rem;
    background: rgba(37, 99, 235, 0.9);
    color: white;
    padding: 0.75rem 1.5rem;
    border-radius: 8px;
    font-weight: 600;
    font-size: 1.1rem;
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
}

/* Charts */
.charts-container {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 2rem;
}

.chart-wrapper {
    background: white;
    border-radius: 16px;
    padding: 1.5rem;
    box-shadow: 0 10px 30px var(--shadow);
}

.chart-wrapper h3 {
    font-size: 1.2rem;
    color: var(--dark);
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

/* Formula Section */
.formula-section {
    background: white;
    border-radius: 16px;
    padding: 2rem;
    box-shadow: 0 10px 30px var(--shadow);
}

.formula-section h3 {
    font-size: 1.3rem;
    color: var(--dark);
    margin-bottom: 1.5rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.formula-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1.5rem;
}

.formula-item {
    padding: 1rem;
    background: linear-gradient(135deg, #667eea10 0%, #764ba210 100%);
    border-radius: 8px;
    border-left: 4px solid var(--primary-color);
}

.formula-item strong {
    display: block;
    color: var(--dark);
    margin-bottom: 0.5rem;
    font-size: 0.95rem;
}

.formula {
    font-family: 'Courier New', monospace;
    background: white;
    padding: 0.75rem;
    border-radius: 6px;
    color: var(--primary-color);
    font-weight: 600;
    font-size: 0.95rem;
}

/* Footer */
footer {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    padding: 2rem 0;
    text-align: center;
    color: var(--gray);
    box-shadow: 0 -4px 6px var(--shadow);
}

/* Responsive Design */
@media (max-width: 1200px) {
    .grid-layout {
        grid-template-columns: 300px 1fr;
    }
    
    .formula-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 968px) {
    .grid-layout {
        grid-template-columns: 1fr;
    }
    
    .control-panel {
        position: relative;
        top: 0;
    }
    
    .charts-container {
        grid-template-columns: 1fr;
    }
    
    header h1 {
        font-size: 2rem;
    }
}

@media (max-width: 640px) {
    header h1 {
        font-size: 1.5rem;
    }
    
    .control-buttons {
        grid-template-columns: 1fr;
    }
    
    #pendulumCanvas {
        height: 400px;
    }
    
    .time-display {
        font-size: 0.9rem;
        padding: 0.5rem 1rem;
    }
}

/* Animations */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.control-panel,
.canvas-container,
.chart-wrapper,
.formula-section {
    animation: fadeIn 0.6s ease-out;
}