:root {
    --bg: #f8fafc;
    --bg-alt: #ffffff;
    --text: #1e293b;
    --text-muted: #64748b;
    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --card-bg: #ffffff;
    --border: #e2e8f0;
    --nav-bg: rgba(255, 255, 255, 0.9);
    
    --success: #10b981;
    --success-bg: #d1fae5;
    --success-light: #ecfdf5;
    
    --warning: #f59e0b;
    --warning-bg: #fef3c7;
    
    --danger: #ef4444;
    --danger-bg: #fee2e2;

    --dark: #0f172a;
    --dark-alt: #1e293b;
    --dark-border: #334155;
}

[data-theme="dark"] {
    --bg: #0f172a;
    --bg-alt: #1e293b;
    --text: #f1f5f9;
    --text-muted: #94a3b8;
    --primary: #3b82f6;
    --primary-hover: #60a5fa;
    --card-bg: #1e293b;
    --border: #334155;
    --nav-bg: rgba(15, 23, 42, 0.9);
    
    --success-bg: rgba(16, 185, 129, 0.2);
    --success-light: rgba(16, 185, 129, 0.1);
    
    --warning-bg: rgba(245, 158, 11, 0.2);
    
    --danger-bg: rgba(239, 68, 68, 0.2);
}

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

body {
    font-family: system-ui, -apple-system, sans-serif;
    background-color: var(--bg);
    color: var(--text);
    line-height: 1.6;
    transition: background-color 0.3s, color 0.3s;
}

a {
    color: inherit;
    text-decoration: none;
}

/* Typography */
h1, h2, h3, h4 {
    line-height: 1.2;
    font-weight: 700;
}
h1 { font-size: 2.5rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.25rem; }

.text-primary { color: var(--primary); }
.text-success { color: var(--success); }
.text-warning { color: var(--warning); }
.text-danger { color: var(--danger); }
.text-muted { color: var(--text-muted); }
.text-white { color: #ffffff; }

.mb-2 { margin-bottom: 0.5rem; }
.mb-4 { margin-bottom: 1.5rem; }
.mt-4 { margin-top: 1.5rem; }
.pt-4 { padding-top: 1.5rem; }

.text-center { text-align: center; }
.text-right { text-align: right; }
.text-left { text-align: left; }
.text-sm { font-size: 0.875rem; }

/* Layout */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.5rem;
}

.grid {
    display: grid;
    gap: 2rem;
}
.grid-2 { grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); }
.grid-3 { grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); }

.flex { display: flex; }
.items-center { align-items: center; }
.justify-center { justify-content: center; }
.gap-2 { gap: 0.5rem; }
.gap-4 { gap: 1rem; }

/* Components */
.icon {
    width: 1.5rem;
    height: 1.5rem;
    display: inline-block;
    vertical-align: middle;
}

.navbar {
    position: sticky;
    top: 0;
    background-color: var(--nav-bg);
    backdrop-filter: blur(8px);
    border-bottom: 1px solid var(--border);
    z-index: 50;
    padding: 1rem 0;
}
.nav-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.brand {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-weight: bold;
    font-size: 1.25rem;
    color: var(--primary);
}
.nav-links {
    display: flex;
    align-items: center;
    gap: 1.5rem;
}
.nav-links a {
    font-weight: 500;
    transition: color 0.2s;
}
.nav-links a:hover {
    color: var(--primary);
}
#theme-toggle {
    background: none;
    border: none;
    cursor: pointer;
    color: var(--text);
    padding: 0.5rem;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background-color 0.2s;
}
#theme-toggle:hover {
    background-color: var(--border);
}

.section {
    padding: 5rem 0;
}
.bg-alt { background-color: var(--bg-alt); }
.bg-dark { background-color: var(--dark); color: #f1f5f9; }
.bg-dark-alt { background-color: var(--dark-alt); }
.bg-success-light { background-color: var(--success-light); }
.border-dark { border-color: var(--dark-border) !important; }

.hero {
    padding: 6rem 0;
    background: linear-gradient(to bottom right, var(--bg), var(--bg-alt));
}
.subtitle {
    font-size: 1.25rem;
    color: var(--text-muted);
    max-width: 800px;
    margin: 0 auto 2rem auto;
}
.badge {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    border-radius: 9999px;
    background-color: var(--primary);
    color: white;
    font-size: 0.875rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
}
.badge-danger { background-color: var(--danger); }

.card {
    background-color: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: 1rem;
    padding: 1.5rem;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.05);
    transition: transform 0.2s, background-color 0.3s, border-color 0.3s;
}
.card:hover {
    transform: translateY(-5px);
}

.circle {
    width: 2rem;
    height: 2rem;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
}
.bg-danger { background-color: var(--danger-bg); }
.bg-warning { background-color: var(--warning-bg); }
.bg-success { background-color: var(--success-bg); }
.bg-primary { background-color: rgba(37, 99, 235, 0.1); }

.icon-circle {
    width: 4rem;
    height: 4rem;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
}

.alert {
    padding: 1rem;
    border-radius: 0.5rem;
    display: flex;
    align-items: flex-start;
    gap: 0.75rem;
    font-weight: 600;
}
.alert-danger {
    background-color: var(--danger-bg);
    color: var(--danger);
    border-left: 4px solid var(--danger);
}
.alert-warning {
    background-color: var(--warning-bg);
    color: var(--warning);
    border-left: 4px solid var(--warning);
}
.inline-block { display: inline-flex; }

/* Symptom Checker */
.checkbox-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
}
.checkbox-label {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 1rem;
    border: 1px solid var(--border);
    border-radius: 0.5rem;
    cursor: pointer;
    background-color: var(--bg);
    transition: all 0.2s;
}
.checkbox-label:hover {
    border-color: var(--primary);
}
.checkbox-label input {
    width: 1.25rem;
    height: 1.25rem;
    cursor: pointer;
}

.btn {
    display: inline-block;
    padding: 0.75rem 2rem;
    border-radius: 9999px;
    font-weight: bold;
    border: none;
    cursor: pointer;
    transition: background-color 0.2s, opacity 0.2s;
}
.btn-primary {
    background-color: var(--primary);
    color: white;
}
.btn-primary:hover:not(:disabled) {
    background-color: var(--primary-hover);
}
.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.result-card {
    padding: 1.5rem;
    border-radius: 1rem;
    border-left: 4px solid transparent;
    display: flex;
    gap: 1rem;
    align-items: flex-start;
}
.result-card.danger {
    background-color: var(--danger-bg);
    border-color: var(--danger);
    color: var(--danger);
}
.result-card.warning {
    background-color: var(--warning-bg);
    border-color: var(--warning);
    color: var(--warning);
}
.result-card.success {
    background-color: var(--success-bg);
    border-color: var(--success);
    color: var(--success);
}
.result-icon-wrapper {
    width: 2rem;
    height: 2rem;
    flex-shrink: 0;
}

/* Footer */
.footer {
    background-color: var(--dark);
    color: var(--text-muted);
    padding: 3rem 0;
    border-top: 1px solid var(--dark-border);
}
.footer .brand {
    color: white;
}
.footer-links {
    list-style: none;
}
.footer-links li {
    margin-bottom: 0.5rem;
}
.footer-links a:hover {
    color: white;
}
.border-t {
    border-top: 1px solid var(--dark-border);
}

/* SVG Illustration Wrapper */
.illustration-container {
    background: linear-gradient(to bottom right, rgba(37, 99, 235, 0.1), rgba(16, 185, 129, 0.1));
    border-radius: 1rem;
    padding: 2rem;
    border: 1px solid var(--border);
}
.svg-wrapper {
    width: 100%;
    aspect-ratio: 4/3;
}

@media (max-width: 768px) {
    h1 { font-size: 2rem; }
    .nav-links a { display: none; }
    #theme-toggle { display: block; }
    .text-right { text-align: left; }
}