:root {
    --bg-color: #f8fafc;
    --container-bg: #ffffff;
    --text-color: #1e293b;
    --text-muted: #64748b;
    --btn-primary: #2563eb;
    --btn-secondary: #f1f5f9;
    --btn-text: #ffffff;
    --border-color: #e2e8f0;
    --accent-color: #3b82f6;
}

[data-theme='dark'] {
    --bg-color: #0f172a;
    --container-bg: #1e293b;
    --text-color: #f8fafc;
    --text-muted: #94a3b8;
    --btn-primary: #3b82f6;
    --btn-secondary: #334155;
    --border-color: #334155;
}

body {
    background-color: var(--bg-color);
    color: var(--text-color);
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    line-height: 1.6;
    margin: 0;
    transition: background-color 0.3s, color 0.3s;
}

.navbar {
    background-color: var(--container-bg);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 1000;
}

.nav-container {
    max-width: 1000px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 1.5rem;
}

.logo {
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--btn-primary);
    text-decoration: none;
}

.nav-menu {
    list-style: none;
    display: flex;
    gap: 1.5rem;
    margin: 0;
    padding: 0;
}

.nav-menu a {
    text-decoration: none;
    color: var(--text-color);
    font-weight: 500;
}

.container {
    max-width: 800px;
    margin: 2rem auto;
    padding: 0 1.5rem;
}

.hero-section {
    text-align: center;
    margin-bottom: 3rem;
}

.hero-section h1 {
    font-size: 2.5rem;
    font-weight: 800;
    margin-bottom: 0.5rem;
}

.hero-subtitle {
    font-size: 1.1rem;
    color: var(--text-muted);
}

.tool-wrapper {
    background-color: var(--container-bg);
    padding: 3rem;
    border-radius: 16px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.05);
    text-align: center;
    border: 1px solid var(--border-color);
    margin-bottom: 3rem;
}

.number {
    font-size: 7rem;
    font-weight: 900;
    color: var(--btn-primary);
    margin-bottom: 2rem;
}

button {
    cursor: pointer;
    border: none;
    border-radius: 8px;
    padding: 0.8rem 1.8rem;
    font-size: 1rem;
    font-weight: 600;
    transition: all 0.2s;
}

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

.sub-btn {
    background-color: var(--btn-secondary);
    color: var(--text-color);
    margin-left: 0.5rem;
}

.article-section {
    background-color: var(--container-bg);
    padding: 2.5rem;
    border-radius: 16px;
    border: 1px solid var(--border-color);
    margin-bottom: 3rem;
}

.feature-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1.5rem;
    margin: 2rem 0;
}

.feature-card {
    padding: 1.5rem;
    background-color: var(--bg-color);
    border-radius: 12px;
}

.feature-card h3 {
    margin-top: 0;
    color: var(--btn-primary);
}

.faq-item {
    margin-bottom: 1.5rem;
}

.contact-section {
    margin-bottom: 3rem;
}

.contact-form {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    margin-top: 1.5rem;
}

.contact-form input, 
.contact-form textarea {
    padding: 1rem;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    background-color: var(--container-bg);
    color: var(--text-color);
}

.site-footer {
    margin-top: 5rem;
    padding: 3rem 0;
    border-top: 1px solid var(--border-color);
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr;
    gap: 2rem;
}

.footer-links a {
    display: block;
    color: var(--text-muted);
    text-decoration: none;
    margin-bottom: 0.5rem;
}

.copyright {
    margin-top: 2rem;
    text-align: center;
    color: var(--text-muted);
    font-size: 0.9rem;
}

.theme-btn-nav {
    font-size: 0.8rem;
    padding: 0.4rem 0.8rem;
    background-color: var(--btn-secondary);
    color: var(--text-color);
}