/* 全局样式 - 移动优先 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', 'Roboto', 'Helvetica Neue', sans-serif;
    line-height: 1.6;
    color: #333;
    background: #f5f5f5;
    min-height: 100vh;
    padding: 20px 10px;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    background: #fff;
    border-radius: 12px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
    overflow: hidden;
    border: 1px solid #e0e0e0;
}

header {
    background: #000;
    color: #fff;
    padding: 50px 20px 30px;
    text-align: center;
    position: relative;
}

.lang-selector {
    position: absolute;
    top: 10px;
    right: 10px;
    display: flex;
    gap: 8px;
    z-index: 1;
}

.lang-btn {
    padding: 6px 12px;
    background: transparent;
    color: #fff;
    border: 1px solid rgba(255,255,255,0.5);
    border-radius: 4px;
    cursor: pointer;
    font-size: 0.85rem;
    transition: all 0.3s;
}

.lang-btn:hover {
    background: rgba(255,255,255,0.1);
}

.lang-btn.active {
    background: #fff;
    color: #000;
    font-weight: 600;
}

h1 {
    font-size: 1.8rem;
    margin-bottom: 10px;
    margin-top: 10px;
}

header p {
    font-size: 0.95rem;
    opacity: 0.9;
    margin-top: 5px;
}

main {
    padding: 30px 20px;
}

section {
    margin-bottom: 40px;
}

h2 {
    color: #000;
    font-size: 1.5rem;
    margin-bottom: 15px;
    border-bottom: 2px solid #000;
    padding-bottom: 8px;
}

.calculator-form {
    background: #fafafa;
    padding: 25px;
    border-radius: 8px;
    margin-bottom: 30px;
    border: 1px solid #e0e0e0;
}

.input-group {
    margin-bottom: 20px;
}

.input-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 600;
    color: #000;
}

.input-wrapper {
    display: flex;
    gap: 10px;
    align-items: center;
}

input[type="number"] {
    flex: 1;
    padding: 12px;
    border: 2px solid #e0e0e0;
    border-radius: 6px;
    font-size: 1rem;
    transition: border-color 0.3s;
}

input[type="number"]:focus {
    outline: none;
    border-color: #000;
}

.unit-toggle {
    display: flex;
    gap: 4px;
}

.calculate-btn {
    width: 100%;
    padding: 14px;
    background: #000;
    color: #fff;
    border: none;
    border-radius: 6px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.3s;
}

.calculate-btn:hover {
    background: #333;
}

.result-container {
    text-align: center;
    padding: 20px;
    background: #000;
    color: #fff;
    border-radius: 8px;
    margin-top: 20px;
}

.bmi-value {
    font-size: 2.5rem;
    font-weight: bold;
    margin: 10px 0;
}

.bmi-category {
    font-size: 1.1rem;
    opacity: 0.9;
}

table {
    width: 100%;
    border-collapse: collapse;
    margin: 20px 0;
    background: #fff;
    border-radius: 8px;
    overflow: hidden;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

th, td {
    padding: 12px 15px;
    text-align: left;
    border-bottom: 1px solid #e0e0e0;
}

th {
    background: #f5f5f5;
    font-weight: 600;
    color: #000;
}

tr:last-child td {
    border-bottom: none;
}

footer {
    text-align: center;
    padding: 20px;
    background: #f5f5f5;
    color: #666;
    font-size: 0.9rem;
}

/* 响应式设计 */
@media (max-width: 600px) {
    body {
        padding: 10px;
    }

    header {
        padding: 30px 15px 20px;
    }

    h1 {
        font-size: 1.5rem;
    }

    .calculator-form {
        padding: 15px;
    }

    .input-wrapper {
        flex-direction: column;
        gap: 5px;
    }

    .unit-toggle {
        width: 100%;
    }

    .unit-btn {
        flex: 1;
        text-align: center;
    }

    table {
        font-size: 0.9rem;
    }

    th, td {
        padding: 8px 10px;
    }
}