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

body {
    font-family: 'Microsoft YaHei', Arial, sans-serif;
    background: linear-gradient(135deg, #a8edea 0%, #fed6e3 100%);
    min-height: 100vh;
    padding: 20px;
}

.container {
    max-width: 600px;
    margin: 0 auto;
    background: white;
    border-radius: 20px;
    box-shadow: 0 25px 50px rgba(0,0,0,0.15);
    overflow: hidden;
}

.header {
    background: linear-gradient(45deg, #667eea, #764ba2);
    color: white;
    padding: 25px 20px;
    text-align: center;
}

.header h1 {
    font-size: 28px;
    margin-bottom: 5px;
}

.header a {
    color: rgba(255,255,255,0.8);
    text-decoration: none;
    font-size: 14px;
}

.calculator {
    padding: 30px;
}

.input-group {
    margin-bottom: 25px;
}

.input-group label {
    display: block;
    margin-bottom: 10px;
    font-weight: 600;
    color: #333;
    font-size: 16px;
}

input, select {
    width: 100%;
    padding: 15px;
    border: 2px solid #e1e8ed;
    border-radius: 12px;
    font-size: 16px;
    transition: all 0.3s;
}

input:focus, select:focus {
    outline: none;
    border-color: #667eea;
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

.button-group {
    display: flex;
    gap: 15px;
    margin: 30px 0;
    flex-wrap: wrap;
}

.btn {
    padding: 15px 20px;
    border: none;
    border-radius: 12px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
    flex: 1;
    min-width: 120px;
}

.btn-calculate {
    background: linear-gradient(45deg, #667eea, #764ba2);
    color: white;
    box-shadow: 0 5px 15px rgba(102, 126, 234, 0.4);
}

.btn-calculate:hover {
    transform: translateY(-3px);
    box-shadow: 0 10px 25px rgba(102, 126, 234, 0.6);
}

.btn-clear {
    background: #ff6b6b;
    color: white;
    box-shadow: 0 5px 15px rgba(255, 107, 107, 0.4);
}

.btn-clear:hover {
    transform: translateY(-3px);
    box-shadow: 0 10px 25px rgba(255, 107, 107, 0.6);
}

.btn-copy {
    background: #4facfe;
    color: white;
    box-shadow: 0 5px 15px rgba(79, 172, 254, 0.4);
}

.btn-copy:hover:not(:disabled) {
    transform: translateY(-3px);
    box-shadow: 0 10px 25px rgba(79, 172, 254, 0.6);
}

.btn-copy:disabled {
    background: #cccccc;
    cursor: not-allowed;
    transform: none;
    box-shadow: none;
}

.result {
    margin-top: 30px;
    padding: 25px;
    background: #f8f9fa;
    border-radius: 15px;
    text-align: center;
    display: none;
}

.result.show {
    display: block;
    animation: fadeIn 0.5s;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}

.bsa-value {
    font-size: 48px;
    font-weight: 700;
    color: #667eea;
    margin: 20px 0 5px 0;
}

.bsa-unit {
    font-size: 20px;
    color: #666;
    margin-bottom: 20px;
}

.result-text {
    font-size: 18px;
    color: #333;
    margin-bottom: 25px;
    font-weight: 500;
}

.reference-info, .formula-info {
    text-align: left;
    margin: 20px 0;
    padding: 15px;
    border-radius: 10px;
}

.reference-info {
    background: #e3f2fd;
    border-left: 4px solid #2196f3;
}

.formula-info {
    background: #f3e5f5;
    border-left: 4px solid #9c27b0;
}

.reference-info h4, .formula-info h4 {
    margin-bottom: 10px;
    color: #333;
}

.reference-info p, .formula-info p {
    font-size: 14px;
    color: #555;
    line-height: 1.5;
    margin: 5px 0;
}

/* 响应式设计 */
@media (max-width: 768px) {
    .container {
        margin: 10px;
        border-radius: 15px;
    }
    
    .header {
        padding: 20px 15px;
    }
    
    .header h1 {
        font-size: 24px;
    }
    
    .calculator {
        padding: 20px;
    }
    
    .button-group {
        flex-direction: column;
    }
    
    .btn {
        width: 100%;
    }
    
    .bsa-value {
        font-size: 36px;
    }
}