:root {
    --primary-color: #007bff;
    --primary-hover: #0056b3;
    --secondary-color: #6c757d;
    --background-color: #f8f9fa;
    --surface-color: #ffffff;
    --text-color: #212529;
    --text-muted: #6c757d;
    --border-color: #dee2e6;
    --success-color: #28a745;
    --error-color: #dc3545;
    --font-family: 'Inter', system-ui, -apple-system, sans-serif;
    --spacing-unit: 1rem;
    --border-radius: 8px;
    --shadow-sm: 0 2px 4px rgba(0,0,0,0.05);
    --shadow-md: 0 4px 6px rgba(0,0,0,0.1);
    --transition-speed: 0.3s;
}

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

body {
    font-family: var(--font-family);
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    margin-bottom: 1rem;
    font-weight: 600;
    color: #1a1a1a;
}

p {
    margin-bottom: 1rem;
}

a {
    color: var(--primary-color);
    text-decoration: none;
    transition: color var(--transition-speed);
}

a:hover {
    color: var(--primary-hover);
    text-decoration: underline;
}

/* Layout */
.container {
    width: 100%;
    max-width: 800px;
    margin: 0 auto;
    padding: 0 var(--spacing-unit);
}

header {
    background-color: var(--surface-color);
    box-shadow: var(--shadow-sm);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.logo img {
    height: 40px;
    width: auto;
}

nav ul {
    display: flex;
    list-style: none;
    gap: 1.5rem;
}

main {
    flex: 1;
    padding: 2rem 0;
}

footer {
    background-color: #343a40;
    color: #f8f9fa;
    padding: 2rem 0;
    margin-top: auto;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 2rem;
}

.footer-section h3 {
    color: #fff;
    font-size: 1.1rem;
    margin-bottom: 1rem;
}

.footer-links {
    list-style: none;
}

.footer-links li {
    margin-bottom: 0.5rem;
}

.footer-links a {
    color: #adb5bd;
}

.footer-links a:hover {
    color: #fff;
}

/* Components */
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    border-radius: var(--border-radius);
    font-weight: 500;
    cursor: pointer;
    border: none;
    transition: all var(--transition-speed);
    font-size: 1rem;
    text-align: center;
}

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

.btn-primary:hover {
    background-color: var(--primary-hover);
    text-decoration: none;
    transform: translateY(-1px);
}

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

.btn-secondary:hover {
    background-color: #5a6268;
    text-decoration: none;
}

.btn-outline {
    background-color: transparent;
    border: 2px solid var(--primary-color);
    color: var(--primary-color);
}

.btn-outline:hover {
    background-color: var(--primary-color);
    color: white;
    text-decoration: none;
}

/* Survey Specifics */
.progress-container {
    background-color: #e9ecef;
    height: 8px;
    border-radius: 4px;
    margin-bottom: 2rem;
    overflow: hidden;
}

.progress-bar {
    height: 100%;
    background-color: var(--success-color);
    width: 0%;
    transition: width 0.5s ease;
}

.question-card {
    background-color: var(--surface-color);
    padding: 2rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
    margin-bottom: 2rem;
}

.question-title {
    font-size: 1.5rem;
    margin-bottom: 1.5rem;
    color: var(--text-color);
}

.options-grid {
    display: grid;
    gap: 1rem;
}

.option-btn {
    background-color: #f8f9fa;
    border: 2px solid var(--border-color);
    padding: 1rem;
    border-radius: var(--border-radius);
    text-align: left;
    cursor: pointer;
    transition: all 0.2s;
    font-size: 1.1rem;
}

.option-btn:hover {
    border-color: var(--primary-color);
    background-color: #e7f1ff;
}

.option-btn.selected {
    border-color: var(--primary-color);
    background-color: var(--primary-color);
    color: white;
}

.navigation-buttons {
    display: flex;
    justify-content: space-between;
    margin-top: 2rem;
}

.content-article {
    background-color: var(--surface-color);
    padding: 2rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-sm);
    margin-top: 3rem;
}

.content-article h2 {
    color: var(--primary-color);
}

/* Utilities */
.text-center { text-align: center; }
.mt-1 { margin-top: 0.25rem; }
.mt-2 { margin-top: 0.5rem; }
.mt-3 { margin-top: 1rem; }
.mt-4 { margin-top: 1.5rem; }
.mb-4 { margin-bottom: 1.5rem; }

/* Responsive */
@media (max-width: 768px) {
    .header-content {
        flex-direction: column;
        gap: 1rem;
    }
    
    nav ul {
        gap: 1rem;
        font-size: 0.9rem;
    }
    
    .question-card {
        padding: 1.5rem;
    }
    
    .question-title {
        font-size: 1.25rem;
    }
}