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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    color: #333;
}

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

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
    background: rgba(255, 255, 255, 0.95);
    padding: 20px;
    border-radius: 15px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
}

h1 {
    color: #2c3e50;
    font-size: 2.5rem;
    font-weight: 600;
}

.language-selector select {
    padding: 10px 15px;
    border: 2px solid #e0e6ed;
    border-radius: 8px;
    background: white;
    font-size: 1rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

.language-selector select:hover {
    border-color: #667eea;
}

.navigation {
    display: flex;
    gap: 10px;
    margin-bottom: 30px;
    background: rgba(255, 255, 255, 0.95);
    padding: 15px;
    border-radius: 15px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
}

.nav-btn {
    flex: 1;
    padding: 15px 20px;
    border: none;
    background: #f8f9fa;
    color: #6c757d;
    border-radius: 10px;
    font-size: 1.1rem;
    cursor: pointer;
    transition: all 0.3s ease;
    font-weight: 500;
}

.nav-btn:hover {
    background: #e9ecef;
    transform: translateY(-2px);
}

.nav-btn.active {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
}

.content {
    background: rgba(255, 255, 255, 0.95);
    border-radius: 15px;
    padding: 30px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
}

.page {
    display: none;
}

.page.active {
    display: block;
}

.calculator h2 {
    color: #2c3e50;
    margin-bottom: 15px;
    font-size: 1.8rem;
    text-align: center;
}

.page-description {
    color: #6c757d;
    font-size: 0.95rem;
    line-height: 1.6;
    margin-bottom: 30px;
    text-align: center;
    padding: 0 20px;
}

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

.input-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 600;
    color: #495057;
    font-size: 1rem;
}

.input-group input {
    width: 100%;
    padding: 12px 15px;
    border: 2px solid #e0e6ed;
    border-radius: 8px;
    font-size: 1rem;
    transition: all 0.3s ease;
}

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

.return-input-group {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 15px;
}

.return-input-group label {
    min-width: 80px;
    font-weight: 600;
    color: #495057;
}

.return-input {
    flex: 1;
    padding: 10px 15px;
    border: 2px solid #e0e6ed;
    border-radius: 8px;
    font-size: 1rem;
}

.remove-btn {
    background: #dc3545;
    color: white;
    border: none;
    border-radius: 50%;
    width: 30px;
    height: 30px;
    cursor: pointer;
    font-size: 1.2rem;
    display: flex;
    align-items: center;
    justify-content: center;
}

.remove-btn:hover {
    background: #c82333;
}

.add-btn {
    background: #28a745;
    color: white;
    border: none;
    padding: 10px 20px;
    border-radius: 8px;
    cursor: pointer;
    font-size: 1rem;
    margin-bottom: 20px;
    transition: all 0.3s ease;
}

.add-btn:hover {
    background: #218838;
    transform: translateY(-2px);
}

.calculate-btn {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    border: none;
    padding: 15px 30px;
    border-radius: 8px;
    font-size: 1.1rem;
    cursor: pointer;
    transition: all 0.3s ease;
    font-weight: 600;
    width: 100%;
    margin-bottom: 30px;
}

.calculate-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
}

.result-section {
    background: #f8f9fa;
    padding: 20px;
    border-radius: 10px;
    border-left: 4px solid #667eea;
}

.result-section h3 {
    color: #2c3e50;
    margin-bottom: 15px;
}

.result-text {
    font-size: 1.2rem;
    font-weight: 600;
    color: #28a745;
}

table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 15px;
}

th, td {
    padding: 12px;
    text-align: center;
    border-bottom: 1px solid #dee2e6;
}

th {
    background: #f1f3f4;
    font-weight: 600;
    color: #495057;
}

tr:hover {
    background: #f8f9fa;
}

@media (max-width: 768px) {
    .container {
        padding: 10px;
    }
    
    header {
        flex-direction: column;
        gap: 15px;
        text-align: center;
    }
    
    h1 {
        font-size: 2rem;
    }
    
    .navigation {
        flex-direction: column;
    }
    
    .return-input-group {
        flex-direction: column;
        align-items: stretch;
    }
    
    .return-input-group label {
        min-width: auto;
    }
}