:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --primary-light: #3b82f6;
    --success: #10b981;
    --warning: #f59e0b;
    --danger: #ef4444;
    --gray-50: #f9fafb;
    --gray-100: #f3f4f6;
    --gray-200: #e5e7eb;
    --gray-300: #d1d5db;
    --gray-400: #9ca3af;
    --gray-500: #6b7280;
    --gray-600: #4b5563;
    --gray-700: #374151;
    --gray-800: #1f2937;
    --gray-900: #111827;
    --white: #ffffff;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
    --shadow-md: 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: 12px;
    --radius-sm: 8px;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: linear-gradient(135deg, #e0e7ff 0%, #c7d2fe 50%, #e0e7ff 100%);
    min-height: 100vh;
    color: var(--gray-800);
    line-height: 1.6;
}

header {
    background: var(--white);
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary);
}

nav {
    display: flex;
    gap: 2rem;
}

nav a {
    color: var(--gray-600);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.2s;
}

nav a:hover {
    color: var(--primary);
}

main {
    max-width: 800px;
    margin: 0 auto;
    padding: 3rem 1.5rem;
}

.hero {
    text-align: center;
    margin-bottom: 2.5rem;
}

.hero h1 {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--gray-900);
    margin-bottom: 0.75rem;
}

.hero p {
    color: var(--gray-600);
    font-size: 1.125rem;
}

.card {
    background: var(--white);
    border-radius: var(--radius);
    box-shadow: var(--shadow-xl);
    padding: 2rem;
}

.form-section {
    margin-bottom: 2rem;
    padding-bottom: 2rem;
    border-bottom: 1px solid var(--gray-200);
}

.form-section:last-of-type {
    border-bottom: none;
    margin-bottom: 1.5rem;
}

.form-section h3 {
    font-size: 1rem;
    font-weight: 600;
    color: var(--gray-700);
    margin-bottom: 1.25rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.form-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1.25rem;
}

.form-row.three-col {
    grid-template-columns: 1fr 1fr;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.form-group label {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--gray-700);
}

.form-group input,
.form-group select {
    padding: 0.75rem 1rem;
    border: 2px solid var(--gray-200);
    border-radius: var(--radius-sm);
    font-size: 1rem;
    font-family: inherit;
    transition: border-color 0.2s, box-shadow 0.2s;
    background: var(--white);
}

.form-group input:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.symptom-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1rem;
}

.checkbox-label {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 1rem;
    border: 2px solid var(--gray-200);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all 0.2s;
}

.checkbox-label:hover {
    border-color: var(--primary-light);
    background: var(--gray-50);
}

.checkbox-label input[type="checkbox"] {
    width: 1.25rem;
    height: 1.25rem;
    accent-color: var(--primary);
    cursor: pointer;
}

.checkbox-label span {
    font-weight: 500;
    color: var(--gray-700);
}

.submit-btn {
    width: 100%;
    padding: 1rem 1.5rem;
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    color: var(--white);
    border: none;
    border-radius: var(--radius-sm);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    transition: all 0.3s;
    box-shadow: var(--shadow-md);
}

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

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

.result-card {
    margin-top: 2rem;
    padding: 1.5rem;
    background: linear-gradient(135deg, #dbeafe 0%, #bfdbfe 100%);
    border: 2px solid var(--primary);
    border-radius: var(--radius-sm);
}

.result-header {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    color: var(--primary-dark);
    font-weight: 600;
    font-size: 0.875rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 1rem;
}

.result-content .prediction {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--gray-900);
    margin-bottom: 0.5rem;
}

.result-content .confidence {
    font-size: 1rem;
    color: var(--gray-700);
}

footer {
    text-align: center;
    padding: 2rem;
    color: var(--gray-500);
    font-size: 0.875rem;
}

@media (max-width: 640px) {
    .header-content {
        padding: 1rem;
    }

    .logo span {
        font-size: 1.25rem;
    }

    nav {
        gap: 1rem;
    }

    main {
        padding: 2rem 1rem;
    }

    .hero h1 {
        font-size: 1.75rem;
    }

    .card {
        padding: 1.5rem;
    }

    .form-row {
        grid-template-columns: 1fr;
    }

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