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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.container {
    background: white;
    border-radius: 20px;
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
    padding: 40px;
    width: 100%;
    max-width: 400px;
    text-align: center;
    animation: slideUp 0.6s ease-out;
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.header {
    margin-bottom: 30px;
}

.app-icon {
    width: 80px;
    height: 80px;
    border-radius: 16px;
    margin-bottom: 15px;
    box-shadow: 0 8px 16px rgba(40, 167, 69, 0.3);
}

h1 {
    color: #2c3e50;
    font-size: 28px;
    font-weight: 700;
    margin-bottom: 10px;
}

.input-section {
    margin-bottom: 30px;
}

label {
    display: block;
    margin-bottom: 12px;
    color: #34495e;
    font-weight: 600;
    font-size: 16px;
}

input[type="number"] {
    width: 100%;
    padding: 16px;
    border: 2px solid #e1e8ed;
    border-radius: 12px;
    font-size: 18px;
    transition: all 0.3s ease;
    background: #f8f9fa;
}

input[type="number"]:focus {
    outline: none;
    border-color: #28a745;
    background: white;
    box-shadow: 0 0 0 3px rgba(40, 167, 69, 0.1);
}

.calculate-btn {
    background: linear-gradient(135deg, #28a745 0%, #20c997 100%);
    color: white;
    padding: 16px 32px;
    border: none;
    border-radius: 12px;
    font-size: 18px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 8px 16px rgba(40, 167, 69, 0.3);
    margin-bottom: 30px;
}

.calculate-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 12px 24px rgba(40, 167, 69, 0.4);
}

.calculate-btn:active {
    transform: translateY(0);
}

.result {
    min-height: 60px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 20px;
    font-weight: 700;
    color: #2c3e50;
    background: #f8f9fa;
    border-radius: 12px;
    padding: 20px;
    margin-bottom: 30px;
    transition: all 0.3s ease;
}

.result.success {
    background: linear-gradient(135deg, #d4edda 0%, #c3e6cb 100%);
    color: #155724;
    border: 2px solid #c3e6cb;
}

.result.error {
    background: linear-gradient(135deg, #f8d7da 0%, #f5c6cb 100%);
    color: #721c24;
    border: 2px solid #f5c6cb;
}

.footer {
    color: #6c757d;
    font-size: 14px;
    font-style: italic;
}

/* Mobile responsiveness */
@media (max-width: 480px) {
    .container {
        padding: 30px 20px;
        margin: 10px;
    }
    
    h1 {
        font-size: 24px;
    }
    
    .app-icon {
        width: 60px;
        height: 60px;
    }
    
    input[type="number"], .calculate-btn {
        font-size: 16px;
    }
}

/* PWA specific styles */
@media (display-mode: standalone) {
    body {
        padding-top: 40px;
    }
}