:root {
    --primary-color: #4a90e2;
    --primary-dark: #357abd;
    --secondary-color: #2c3e50;
    --accent-color: #e74c3c;
    --background-color: #f5f6fa;
    --text-color: #2c3e50;
    --border-color: #dcdde1;
    --success-color: #2ecc71;
    --card-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background: var(--background-color);
}

header {
    background: #4a90e2;
    color: white;
    text-align: center;
    padding: 1rem;
    margin-bottom: 1rem;
}

header h1 {
    font-size: 1.25rem;
    margin-bottom: 0.25rem;
}

header .subtitle {
    font-size: 0.85rem;
    opacity: 0.9;
}

main {
    max-width: 800px;
    margin: 0 auto;
    padding: 0 1rem;
}

.calculator-container {
    background: white;
    border-radius: 10px;
    padding: 2rem;
    box-shadow: var(--card-shadow);
    margin-bottom: 2rem;
}

.unit-toggle {
    display: flex;
    justify-content: center;
    margin-bottom: 2rem;
    gap: 0.5rem;
    background: none;
}

.unit-btn {
    flex: 1;
    max-width: 160px;
    padding: 0.75rem;
    border: 1px solid #4a90e2;
    background: white;
    color: #4a90e2;
    border-radius: 25px;
    cursor: pointer;
    transition: all 0.3s ease;
    font-size: 0.95rem;
}

.unit-btn.active {
    background: #4a90e2;
    color: white;
}

.form-group {
    display: grid;
    gap: 0.5rem;
    margin-bottom: 1.25rem;
}

label {
    font-weight: 500;
    color: #333;
    font-size: 0.9rem;
}

input, select {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid #ddd;
    border-radius: 8px;
    font-size: 1rem;
    background: white;
}

.gender-buttons {
    display: flex;
    gap: 0.5rem;
}

.gender-btn {
    flex: 1;
    padding: 0.75rem;
    border: 1px solid #ddd;
    background: white;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s ease;
    font-size: 0.95rem;
    color: #333;
}

.gender-btn.active {
    background: #4a90e2;
    color: white;
    border-color: #4a90e2;
}

.activity-description {
    font-size: 0.85rem;
    color: #666;
    margin-top: 0.3rem;
}

.calculate-btn {
    background: var(--primary-color);
    color: white;
    border: none;
    padding: 0.6rem;
    border-radius: 6px;
    font-size: 1rem;
    cursor: pointer;
    transition: background-color 0.3s ease;
    margin-top: 0.5rem;
}

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

.results-section {
    margin-top: 2rem;
    text-align: center;
}

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

.result-item {
    background: #f8f9fa;
    padding: 1.5rem;
    border-radius: 8px;
    box-shadow: var(--card-shadow);
}

.result-item h3 {
    color: var(--secondary-color);
    font-size: 1.1rem;
    margin-bottom: 1rem;
}

.result-item p {
    font-size: 2rem;
    font-weight: bold;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.result-item .unit {
    font-size: 0.9rem;
    color: #666;
}

.faq-section {
    margin: 3rem 0;
    background: white;
    border-radius: 10px;
    padding: 2rem;
    box-shadow: var(--card-shadow);
}

.faq-container {
    display: grid;
    margin-top: 1rem;
    gap: 1rem;
}

details {
    background: white;
    padding: 1rem;
    border-radius: 8px;
    box-shadow: var(--card-shadow);
}

summary {
    font-weight: 600;
    cursor: pointer;
    padding: 0.5rem 0;
}

details p {
    margin-top: 1rem;
    color: #666;
}

footer {
    background: var(--secondary-color);
    color: white;
    padding: 2rem 1rem;
    margin-top: 3rem;
}

.footer-content {
    max-width: 800px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
}

.footer-links {
    display: flex;
    gap: 2rem;
}

.footer-links a {
    color: white;
    text-decoration: none;
    opacity: 0.8;
    transition: opacity 0.3s ease;
}

.footer-links a:hover {
    opacity: 1;
}

@media (max-width: 600px) {
    body {
        background: #f5f6fa;
    }

    header {
        padding: 0.75rem;
        margin-bottom: 0;
    }

    header h1 {
        font-size: 1.25rem;
        margin-bottom: 0.25rem;
    }

    header .subtitle {
        font-size: 0.8rem;
        opacity: 0.9;
    }

    main {
        padding: 0 1rem;
    }

    .calculator-container {
        padding: 1.25rem;
        margin: 0 -1rem;
        border-radius: 0;
        box-shadow: none;
        background: white;
    }

    .unit-toggle {
        margin-bottom: 1.5rem;
    }

    .unit-btn {
        padding: 0.6rem;
        font-size: 0.9rem;
        border-width: 1px;
    }

    .form-group {
        margin-bottom: 1rem;
    }

    label {
        font-size: 0.9rem;
        margin-bottom: 0.25rem;
    }

    input, select {
        font-size: 1rem;
        padding: 0.75rem;
        border: 1px solid #ddd;
        background: white;
    }

    .gender-buttons {
        gap: 0.5rem;
    }

    .gender-btn {
        padding: 0.75rem;
        font-size: 0.9rem;
    }

    select {
        appearance: none;
        background-image: url("data:image/svg+xml;charset=UTF-8,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='currentColor' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3e%3cpolyline points='6 9 12 15 18 9'%3e%3c/polyline%3e%3c/svg%3e");
        background-repeat: no-repeat;
        background-position: right 1rem center;
        background-size: 1em;
    }

    .activity-description {
        font-size: 0.8rem;
        color: #666;
        margin-top: 0.25rem;
        padding: 0 0.25rem;
    }

    .calculate-btn {
        width: 100%;
        padding: 0.75rem;
        font-size: 1rem;
        margin-top: 0.5rem;
    }

    .result-card {
        grid-template-columns: 1fr;
        gap: 1rem;
    }

    .result-item {
        padding: 1rem;
    }

    .result-item h3 {
        font-size: 1rem;
    }

    .result-item p {
        font-size: 1.75rem;
    }

    .footer-links {
        flex-direction: column;
        gap: 0.75rem;
        text-align: center;
    }
}

/* 添加中等屏幕的断点 */
@media (min-width: 601px) and (max-width: 768px) {
    main {
        padding: 0 1rem;
    }

    .calculator-container {
        padding: 1.5rem;
    }

    .unit-toggle {
        width: auto;
        margin: 0 auto 1.5rem;
    }
}