:root {
    --primary-color: #6366f1;
    --primary-hover: #4f46e5;
    --primary-light: #e0e7ff;
    --secondary-color: #64748b;
    --background: #f8fafc;
    --surface: #ffffff;
    --surface-hover: #f1f5f9;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-muted: #94a3b8;
    --border: #e2e8f0;
    --border-light: #f1f5f9;
    --success: #10b981;
    --warning: #f59e0b;
    --error: #ef4444;
    --info: #3b82f6;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
    --radius: 0.75rem;
    --radius-lg: 1rem;
    --radius-xl: 1.5rem;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: linear-gradient(135deg, #727580 0%, #bcb5c2 100%);
    min-height: 100vh;
    color: var(--text-primary);
    line-height: 1.6;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem;
    min-height: 100vh;
}

/* Header */
.main-header {
    text-align: center;
    margin-bottom: 3rem;
}

.main-header h1 {
    font-size: 3rem;
    font-weight: 800;
    color: white;
    margin-bottom: 0.5rem;
    text-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

.main-header .icon {
    display: block;
    font-size: 4rem;
    margin-bottom: 1rem;
    animation: bounce 2s infinite;
}

.main-header .subtitle {
    display: block;
    font-size: 1.25rem;
    font-weight: 400;
    color: rgba(255, 255, 255, 0.9);
    margin-top: 0.5rem;
}

@keyframes bounce {
    0%, 20%, 53%, 80%, 100% {
        transform: translate3d(0,0,0);
    }
    40%, 43% {
        transform: translate3d(0, -8px, 0);
    }
    70% {
        transform: translate3d(0, -4px, 0);
    }
    90% {
        transform: translate3d(0, -2px, 0);
    }
}

/* Calculator Section */
.calculator-section {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    margin-bottom: 3rem;
}

.form-container, .results-container {
    background: var(--surface);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-xl);
    padding: 2rem;
    backdrop-filter: blur(10px);
}

.form-container h2, .results-container h2 {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 1.5rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

/* Form Styles */
.form-grid {
    display: grid;
    gap: 1.5rem;
    margin-bottom: 2rem;
}

.form-group {
    position: relative;
}

.form-group label {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
    font-size: 0.875rem;
}

.label-icon {
    font-size: 1rem;
}

.form-control {
    width: 100%;
    padding: 0.875rem 1rem;
    border: 2px solid var(--border);
    border-radius: var(--radius);
    font-size: 1rem;
    transition: all 0.2s ease;
    background: var(--surface);
    color: var(--text-primary);
}

.form-control:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.form-control::placeholder {
    color: var(--text-muted);
}

/* Tooltip */
.tooltip {
    position: relative;
    display: inline-block;
}

.tooltip-icon {
    cursor: help;
    opacity: 0.7;
}

.tooltip-content {
    visibility: hidden;
    opacity: 0;
    position: absolute;
    bottom: 125%;
    left: 50%;
    transform: translateX(-50%);
    background: var(--text-primary);
    color: white;
    padding: 0.75rem;
    border-radius: var(--radius);
    font-size: 0.813rem;
    white-space: nowrap;
    z-index: 1000;
    transition: opacity 0.2s;
    box-shadow: var(--shadow-lg);
}

.tooltip:hover .tooltip-content {
    visibility: visible;
    opacity: 1;
}

/* Buttons */
.button-group {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.875rem 1.5rem;
    border: none;
    border-radius: var(--radius);
    font-size: 1rem;
    font-weight: 600;
    text-decoration: none;
    cursor: pointer;
    transition: all 0.2s ease;
    white-space: nowrap;
    min-height: 44px;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
    box-shadow: var(--shadow);
}

.btn-primary:hover {
    background: var(--primary-hover);
    transform: translateY(-1px);
    box-shadow: var(--shadow-lg);
}

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

.btn-secondary:hover {
    background: #475569;
    transform: translateY(-1px);
}

.btn-small {
    padding: 0.5rem 1rem;
    font-size: 0.875rem;
}

/* Results Section */
.results-content {
    min-height: 400px;
}

.empty-state {
    text-align: center;
    padding: 3rem 1rem;
    color: var(--text-muted);
}

.empty-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.empty-state h3 {
    font-size: 1.25rem;
    margin-bottom: 0.5rem;
    color: var(--text-secondary);
}

/* Results Display */
.results-header {
    text-align: center;
    margin-bottom: 2rem;
}

.results-header h2 {
    font-size: 1.5rem;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.test-info {
    color: var(--text-secondary);
    font-size: 1rem;
}

.statistics-summary {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 1rem;
    margin-bottom: 2rem;
    padding: 1.5rem;
    background: var(--primary-light);
    border-radius: var(--radius-lg);
}

.stat-item {
    text-align: center;
}

.stat-item strong {
    display: block;
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-bottom: 0.25rem;
}

.stat-item span {
    display: block;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

/* Results Table */
.results-table-container {
    overflow-x: auto;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    margin-bottom: 2rem;
}

.results-table {
    width: 100%;
    border-collapse: collapse;
    background: var(--surface);
}

.results-table th,
.results-table td {
    padding: 1rem;
    text-align: left;
    border-bottom: 1px solid var(--border-light);
}

.results-table th {
    background: var(--surface-hover);
    font-weight: 600;
    color: var(--text-primary);
    font-size: 0.875rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.results-table tr:hover {
    background: var(--surface-hover);
}

.rpe-row {
    background: var(--primary-light) !important;
}

.average-row {
    background: var(--surface-hover) !important;
    font-weight: 600;
}

.method-name {
    max-width: 200px;
}

.method-label {
    display: block;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.25rem;
}

.method-name small {
    display: block;
    color: var(--text-muted);
    font-size: 0.75rem;
}

.result-value {
    font-weight: 700;
    color: var(--primary-color);
    font-size: 1.1rem;
}

/* Reliability Badges */
.reliability-badge {
    display: inline-flex;
    align-items: center;
    padding: 0.375rem 0.75rem;
    font-size: 0.75rem;
    font-weight: 600;
    border-radius: 9999px;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.reliability-badge.high {
    background: #dcfce7;
    color: #166534;
}

.reliability-badge.good {
    background: #fef3c7;
    color: #92400e;
}

.reliability-badge.average {
    background: #fee4e2;
    color: #991b1b;
}

/* Deviation Values */
.deviation-value.low {
    color: var(--success);
}

.deviation-value.medium {
    color: var(--warning);
}

.deviation-value.high {
    color: var(--error);
}

/* Recommendations */
.recommendations {
    background: var(--surface-hover);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    margin-top: 2rem;
}

.recommendations h4 {
    color: var(--text-primary);
    margin-bottom: 1rem;
    font-size: 1.125rem;
}

.recommendations ul {
    list-style: none;
}

.recommendations li {
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--border-light);
}

.recommendations li:last-child {
    border-bottom: none;
}

/* Formulas Section */
.formulas-section {
    background: var(--surface);
    border-radius: var(--radius-xl);
    padding: 2rem;
    margin-bottom: 2rem;
    box-shadow: var(--shadow-xl);
}

.formulas-section h2 {
    font-size: 1.875rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 2rem;
    text-align: center;
}

.formula-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.5rem;
    margin-bottom: 3rem;
}

.formula-card {
    background: var(--surface);
    border: 2px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    transition: all 0.2s ease;
    position: relative;
    overflow: hidden;
}

.formula-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

.formula-card.featured {
    border-color: var(--primary-color);
    background: linear-gradient(135deg, var(--primary-light) 0%, var(--surface) 100%);
}

.formula-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 1rem;
}

.formula-header h3 {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
}

.formula-badge {
    padding: 0.25rem 0.75rem;
    font-size: 0.75rem;
    font-weight: 600;
    border-radius: 9999px;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.formula-badge.recommended {
    background: #dcfce7;
    color: #166534;
}

.formula-badge.popular {
    background: #dbeafe;
    color: #1e40af;
}

.formula-badge {
    background: var(--surface-hover);
    color: var(--text-secondary);
}

.formula-math {
    background: var(--surface-hover);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1rem;
    margin-bottom: 1rem;
    font-family: 'Monaco', 'Menlo', monospace;
    font-size: 0.875rem;
    color: var(--primary-color);
    word-break: break-all;
}

.formula-details {
    display: grid;
    gap: 0.5rem;
}

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

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

.detail-label {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.detail-value {
    font-weight: 600;
    color: var(--text-primary);
}

/* Info Section */
.info-section {
    margin-top: 2rem;
}

.info-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1.5rem;
}

.info-card {
    background: var(--surface-hover);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    text-align: center;
}

.info-icon {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.info-card h4 {
    font-size: 1.125rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 1rem;
}

.info-card ul {
    list-style: none;
    text-align: left;
}

.info-card li {
    padding: 0.5rem 0;
    color: var(--text-secondary);
}

/* Footer */
footer {
    text-align: center;
    padding: 2rem;
    color: rgba(255, 255, 255, 0.8);
    font-size: 0.875rem;
}

/* Responsive Design */
@media (max-width: 768px) {
    .container {
        padding: 1rem;
    }
    
    .main-header h1 {
        font-size: 2rem;
    }
    
    .calculator-section {
        grid-template-columns: 1fr;
    }
    
    .form-grid {
        grid-template-columns: 1fr;
    }
    
    .button-group {
        flex-direction: column;
    }
    
    .statistics-summary {
        grid-template-columns: 1fr;
    }
    
    .results-table {
        font-size: 0.875rem;
    }
    
    .results-table th,
    .results-table td {
        padding: 0.75rem 0.5rem;
    }
    
    .formula-grid {
        grid-template-columns: 1fr;
    }
    
    .info-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    .main-header h1 {
        font-size: 1.5rem;
    }
    
    .main-header .icon {
        font-size: 2.5rem;
    }
    
    .form-container,
    .results-container,
    .formulas-section {
        padding: 1rem;
    }
    
    .btn {
        padding: 0.75rem 1rem;
    }
}

/* Smooth scrolling and animations */
html {
    scroll-behavior: smooth;
}

.form-control,
.btn,
.formula-card {
    transition: all 0.2s ease;
}

/* Loading animation */
.loading {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 2px solid rgba(255, 255, 255, 0.3);
    border-radius: 50%;
    border-top-color: #fff;
    animation: spin 1s ease-in-out infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}