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

body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color: #f0f2f5;
}

.login-container {
    background: white;
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    width: 100%;
    max-width: 400px;
}

.login-header {
    text-align: center;
    margin-bottom: 2rem;
}

.login-header h2 {
    color: #333;
    margin-bottom: 0.5rem;
}

.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    color: #666;
    font-size: 0.9rem;
}

.form-group input {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid #ddd;
    border-radius: 4px;
    font-size: 1rem;
    transition: border-color 0.3s;
}

.form-group input:focus {
    outline: none;
    border-color: #007bff;
}

.btn-submit {
    width: 100%;
    padding: 0.75rem;
    background-color: #007bff;
    color: white;
    border: none;
    border-radius: 4px;
    font-size: 1rem;
    cursor: pointer;
    transition: background-color 0.3s;
    position: relative;
}

.btn-submit:hover {
    background-color: #0056b3;
}

.btn-submit:disabled {
    background-color: #ccc;
    cursor: not-allowed;
}

/* Thông báo lỗi/thành công */
#message {
    margin-top: 1rem;
    padding: 0.75rem;
    border-radius: 4px;
    text-align: center;
    font-size: 0.9rem;
    display: none; /* Ẩn mặc định */
}

.success {
    background-color: #d4edda;
    color: #155724;
    border: 1px solid #c3e6cb;
}

.error {
    background-color: #f8d7da;
    color: #721c24;
    border: 1px solid #f5c6cb;
}

/* Animation xoay tròn khi loading */
.spinner {
    display: none;
    width: 16px;
    height: 16px;
    border: 2px solid #ffffff;
    border-top: 2px solid transparent;
    border-radius: 50%;
    animation: spin 1s linear infinite;
    position: absolute;
    right: 15px;
    top: 50%;
    transform: translateY(-50%);
}

@keyframes spin {
    0% { transform: translateY(-50%) rotate(0deg); }
    100% { transform: translateY(-50%) rotate(360deg); }
}