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

:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --secondary: #10b981;
    --text: #1f2937;
    --text-light: #6b7280;
    --bg: #f9fafb;
    --card-bg: #ffffff;
    --border: #e5e7eb;
    --shadow: 0 1px 3px rgba(0,0,0,0.1);
    --shadow-lg: 0 10px 25px rgba(0,0,0,0.1);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    -webkit-text-size-adjust: 100%;
    text-size-adjust: 100%;
}

body > header,
body > main,
body > footer,
body > .hero {
    width: 100%;
}

body > main {
    flex-grow: 1;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
header {
    background: var(--card-bg);
    border-bottom: 1px solid var(--border);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: var(--shadow);
}

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

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary);
    text-decoration: none;
    flex-shrink: 0;
}

nav {
    display: flex;
    align-items: center;
}

nav a {
    color: var(--text);
    text-decoration: none;
    margin-left: 2rem;
    font-weight: 500;
    transition: color 0.2s;
    white-space: nowrap;
    flex-shrink: 0;
}

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

nav a.active {
    color: var(--primary);
    font-weight: 500;
    position: relative;
}

nav a.active::after {
    content: '';
    position: absolute;
    bottom: -0.5rem;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--primary);
}

/* Hero */
.hero {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    color: white;
    padding: 4rem 0;
    text-align: center;
}

.hero h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.hero p {
    font-size: 1.2rem;
    opacity: 0.9;
}

/* Calculator Grid */
.calc-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1.5rem;
    padding: 3rem 0;
}

.calc-card {
    background: var(--card-bg);
    border-radius: 12px;
    padding: 2rem;
    text-align: center;
    text-decoration: none;
    color: var(--text);
    transition: all 0.3s;
    border: 1px solid var(--border);
    box-shadow: var(--shadow);
}

.calc-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary);
}

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

.calc-card h3 {
    font-size: 1.25rem;
    margin-bottom: 0.5rem;
    color: var(--text);
}

.calc-card p {
    color: var(--text-light);
    font-size: 0.9rem;
}

/* Calculator Page */
.calc-page {
    padding: 3rem 0;
}

.calc-header {
    text-align: center;
    margin-bottom: 2rem;
}

.calc-header h1 {
    font-size: 2rem;
    margin-bottom: 0.5rem;
}

.calc-header p {
    color: var(--text-light);
}

.calc-container {
    max-width: 800px;
    margin: 0 auto;
    background: var(--card-bg);
    border-radius: 12px;
    padding: 2rem;
    box-shadow: var(--shadow);
    border: 1px solid var(--border);
}

.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--text);
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--border);
    border-radius: 8px;
    font-size: 1rem;
    transition: border-color 0.2s;
}

.form-group input:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--primary);
}

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

#langToggle {
    appearance: none;
    -webkit-appearance: none;
    -moz-appearance: none;
}

.btn {
    background: var(--primary);
    color: white;
    border: none;
    padding: 0.75rem 2rem;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.2s;
    width: 100%;
}

.btn:hover {
    background: var(--primary-dark);
}

.btn-reset {
    background: var(--text-light);
    margin-top: 0.5rem;
}

.btn-reset:hover {
    background: #4b5563;
}

/* Result */
.result {
    margin-top: 2rem;
    padding: 1.5rem;
    background: #f0f9ff;
    border-radius: 8px;
    border-left: 4px solid var(--primary);
    display: none;
}

.result.show {
    display: block;
}

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

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

.result-label {
    color: var(--text-light);
}

.result-value {
    font-weight: 600;
    color: var(--primary);
    font-size: 1.1rem;
}

.result-total {
    font-size: 1.5rem;
    color: var(--secondary);
}

/* Content Sections */
.content-section {
    max-width: 800px;
    margin: 2rem auto 0;
}

.content-section h2 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
    color: var(--text);
    border-bottom: 2px solid var(--primary);
    padding-bottom: 0.5rem;
}

.content-section h3 {
    font-size: 1.15rem;
    margin: 1.5rem 0 0.5rem;
    color: var(--text);
}

.content-section p {
    color: var(--text-light);
    margin-bottom: 1rem;
    line-height: 1.8;
}

.formula-box {
    background: #f0f4ff;
    border: 1px solid #c7d2fe;
    border-radius: 8px;
    padding: 1.5rem;
    margin: 1rem 0;
    font-family: 'Courier New', monospace;
    font-size: 0.95rem;
    color: var(--text);
    overflow-x: auto;
}

.example-box {
    background: #f0fdf4;
    border: 1px solid #bbf7d0;
    border-radius: 8px;
    padding: 1.5rem;
    margin: 1rem 0;
}

.example-box strong {
    color: var(--secondary);
}

.faq-section {
    margin-top: 2rem;
}

.faq-item {
    border-bottom: 1px solid var(--border);
    padding: 1rem 0;
}

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

.faq-q {
    font-weight: 600;
    color: var(--text);
    margin-bottom: 0.5rem;
    cursor: pointer;
}

.faq-q::before {
    content: 'Q: ';
    color: var(--primary);
}

.faq-a {
    color: var(--text-light);
    line-height: 1.8;
}

.faq-a::before {
    content: 'A: ';
    color: var(--secondary);
    font-weight: 600;
}

.related-calcs {
    margin-top: 2rem;
    padding: 1.5rem;
    background: var(--card-bg);
    border-radius: 12px;
    border: 1px solid var(--border);
}

.related-calcs h3 {
    margin-top: 0;
}

.related-calcs a {
    display: inline-block;
    margin: 0.3rem 0.5rem 0.3rem 0;
    padding: 0.4rem 1rem;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 20px;
    color: var(--primary);
    text-decoration: none;
    font-size: 0.9rem;
    transition: all 0.2s;
}

.related-calcs a:hover {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
}

/* Related calculators - alternate class names */
.related-calculators {
    margin-top: 2rem;
    padding: 1.5rem;
    background: var(--card-bg);
    border-radius: 12px;
    border: 1px solid var(--border);
}

.related-calculators h2,
.related-calculators h3 {
    margin-top: 0;
    margin-bottom: 1rem;
}

.related-links,
.related-link {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-top: 0.5rem;
}

.related-links a,
.related-link a,
.related-calculators a {
    display: inline-block;
    padding: 0.5rem 1rem;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 20px;
    color: var(--primary);
    text-decoration: none;
    font-size: 0.9rem;
    transition: all 0.2s;
    white-space: nowrap;
}

.related-links a:hover,
.related-link a:hover,
.related-calculators a:hover {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
}

/* Bilingual content visibility */
[data-lang] {
    display: none;
}

/* Footer */
footer {
    background: var(--card-bg);
    border-top: 1px solid var(--border);
    padding: 2rem 0;
    margin-top: 4rem;
    text-align: center;
    color: var(--text-light);
}

/* Responsive */
@media (max-width: 768px) {
    .hero {
        display: none;
    }

    .logo {
        font-size: 1.1rem;
        flex-shrink: 0;
        display: flex;
        flex-direction: column;
        line-height: 1.2;
    }

    .logo-line1,
    .logo-sub {
        display: block;
        white-space: nowrap;
    }

    .logo-sub {
        padding-left: 0.15em;
    }

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

    .calc-page {
        padding: 0;
    }

    .calc-header {
        margin-bottom: 0.8rem;
    }

    .form-row {
        align-items: stretch;
    }

    /* 移动端导航不换行，可横向滚动 */
    header .container {
        flex-wrap: nowrap;
    }
    
    nav {
        display: flex;
        align-items: center;
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
        scrollbar-width: none;
    }
    
    nav::-webkit-scrollbar {
        display: none;
    }
    
    nav a {
        margin-left: 0.8rem;
        font-size: 1.2rem;
        white-space: nowrap;
        flex-shrink: 0;
    }
    
    nav a.active {
        font-size: 1.2rem;
    }
    
    nav a:first-child {
        margin-left: 1rem;
    }
    
    [data-site-lang="en"] nav a:first-child {
        margin-left: 1rem;
    }
    
    #langToggle {
        flex-shrink: 0;
        font-size: 0.8rem !important;
        padding: 0.3rem 0.6rem !important;
    }
    
    .calc-grid {
        grid-template-columns: 1fr 1fr;
        gap: 0.8rem;
        padding: 1rem 0;
    }

    .calc-card p {
        display: none;
    }

    .calc-card {
        aspect-ratio: 1 / 1;
        padding: 1rem;
        display: flex;
        flex-direction: column;
        justify-content: center;
        overflow: hidden;
    }

    .calc-card h3 {
        font-size: 0.9rem;
        word-break: break-word;
        overflow-wrap: break-word;
    }
    
    .content-section {
        padding: 0 0.5rem;
    }
    
    .formula-box {
        font-size: 0.85rem;
        padding: 1rem;
    }
    
    /* 移动端表单间距缩小 */
    .form-group {
        margin-bottom: .5rem;
    }
    
    .form-group input,
    .form-group select {
        padding: 0.6rem;
        font-size: 0.9rem;
    }
    
    .form-group label {
        font-size: 0.8rem;
        margin-bottom: 0.3rem;
    }
    
    .calc-container {
        padding: 1rem;
    }
    
    .btn {
        padding: 0.6rem 1.5rem;
        font-size: 0.9rem;
    }
    
    .result {
        padding: 1rem;
        margin-top: 1.2rem;
    }
    
    .result-item {
        padding: 0.4rem 0;
    }
    
    /* 手机端英文样式调整 */
    [data-site-lang="en"] .logo-sub {
        padding-left: 0;
    }
    
    [data-site-lang="en"] .form-group label {
        font-size: 0.74rem;
    }
}