* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

html, body {
    height: 100%;
    margin: 0;
    padding: 0;
}

body {
    background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    flex-direction: column;
}


.container {
    background-color: white;
    padding: 2.5rem;
    border-radius: 12px;
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
    width: 90%;
    max-width: 450px;
    text-align: center;
}

h2 {
    color: #333;
    margin-bottom: 1.5rem;
    font-size: 1.8rem;
    position: relative;
    padding-bottom: 10px;
}

.container h2:after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 50px;
    height: 3px;
    background-color: #4a6cf7;
}

form {
    margin-top: 2rem;
}

input[type="text"] {
    width: 100%;
    padding: 15px;
    border: 1px solid #ddd;
    border-radius: 8px;
    font-size: 1rem;
    margin-bottom: 1.5rem;
    transition: border-color 0.3s;
    text-align: center;
    letter-spacing: 2px;
}

input[type="text"]:focus {
    border-color: #4a6cf7;
    outline: none;
    box-shadow: 0 0 0 2px rgba(74, 108, 247, 0.2);
}

button {
    background-color: #4a6cf7;
    color: white;
    border: none;
    padding: 15px 30px;
    border-radius: 8px;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 600;
    transition: background-color 0.3s;
    width: 100%;
}

button:hover {
    background-color: #3a5bd9;
}

.error {
    color: #e74c3c;
    margin-top: 1rem;
    font-size: 0.9rem;
    background-color: #fdecea;
    padding: 10px;
    border-radius: 6px;
    border-left: 4px solid #e74c3c;
    text-align: left;
}

.key-icon {
    display: block;
    margin: 0 auto 1.5rem;
    width: 60px;
    height: 60px;
    background-color: #f0f4ff;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
}

.key-icon svg {
    width: 30px;
    height: 30px;
    fill: #4a6cf7;
}
button#createKey {
    background-color: #4CAF50; /* Màu xanh lá */
    color: white;
    padding: 10px 20px;
    margin-top: 10px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-size: 16px;
    transition: background-color 0.3s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 5px;
}

button#createKey:hover {
    background-color: #45a049;
}

@media (max-width: 480px) {
    .container {
        padding: 1.5rem;
    }
    
    h2 {
        font-size: 1.5rem;
    }
}