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

:root {
    --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --primary-color: #667eea;
    --primary-dark: #764ba2;
    --success-bg: #d4edda;
    --success-color: #155724;
    --success-border: #c3e6cb;
    --error-bg: #f8d7da;
    --error-color: #721c24;
    --error-border: #f5c6cb;
    --input-bg: #f8f9fa;
    --input-border: #e0e0e0;
    --shadow-light: rgba(0, 0, 0, 0.1);
    --shadow-medium: rgba(0, 0, 0, 0.3);
    --shadow-primary: rgba(102, 126, 234, 0.4);
    --transition-smooth: all 0.3s ease;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: var(--primary-gradient);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.container {
    background: white;
    border-radius: 20px;
    box-shadow: 0 20px 60px var(--shadow-medium);
    padding: 40px;
    max-width: 500px;
    width: 100%;
    animation: fadeIn 0.5s ease;
}

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

h1 {
    color: #333;
    margin-bottom: 10px;
    font-size: 28px;
    text-align: center;
}

.subtitle {
    color: #666;
    text-align: center;
    margin-bottom: 30px;
    font-size: 14px;
}

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

label {
    display: block;
    color: #555;
    font-weight: 600;
    margin-bottom: 8px;
    font-size: 14px;
}

input[type="text"],
input[type="number"] {
    width: 100%;
    padding: 12px 15px;
    border: 2px solid var(--input-border);
    border-radius: 10px;
    font-size: 15px;
    transition: var(--transition-smooth);
    background: var(--input-bg);
}

input:focus {
    outline: none;
    border-color: var(--primary-color);
    background: white;
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

input:invalid:not(:placeholder-shown) {
    border-color: #dc3545;
}

.dimension-group {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr;
    gap: 15px;
}

.feature-group {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 15px;
}

button {
    width: 100%;
    padding: 15px;
    background: var(--primary-gradient);
    color: white;
    border: none;
    border-radius: 10px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
    margin-top: 10px;
    position: relative;
}

button:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 10px 25px var(--shadow-primary);
}

button:active:not(:disabled) {
    transform: translateY(0);
}

button:disabled {
    opacity: 0.7;
    cursor: not-allowed;
}

.spinner {
    animation: spin 1s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

.message {
    padding: 15px;
    border-radius: 10px;
    margin-bottom: 20px;
    display: none;
    animation: slideDown 0.3s ease;
}

@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.message.show {
    display: block;
}

.success-message {
    background: var(--success-bg);
    color: var(--success-color);
    border: 1px solid var(--success-border);
}

.error-message {
    background: var(--error-bg);
    color: var(--error-color);
    border: 1px solid var(--error-border);
}

.icon {
    margin-right: 5px;
}

@media (max-width: 600px) {
    .dimension-group {
        grid-template-columns: 1fr;
    }
    
    .feature-group {
        grid-template-columns: 1fr;
    }
    
    .container {
        padding: 30px 20px;
    }
    
    h1 {
        font-size: 24px;
    }
}