body {
    background: linear-gradient(135deg, #4facfe, #00f2fe);
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    font-family: Arial, sans-serif;
}

.login-box {
    background: #fff;
    padding: 30px 25px;
    border-radius: 12px;
    width: 320px;
    box-shadow: 0 10px 25px rgba(0,0,0,0.2);
}

    .login-box h2 {
        text-align: center;
        margin-bottom: 20px;
    }

.input-group {
    position: relative;
    margin-bottom: 18px;
}

    .input-group input {
        width: 100%;
        padding: 10px;
        border: 1px solid #ccc;
        border-radius: 6px;
        outline: none;
        transition: all 0.3s ease;
    }

        /* hiệu ứng focus */
        .input-group input:focus {
            border-color: #4facfe;
            box-shadow: 0 0 8px rgba(79,172,254,0.5);
            transform: scale(1.02);
        }

.btn-login {
    width: 100%;
    padding: 10px;
    border: none;
    background: #4facfe;
    color: white;
    border-radius: 6px;
    cursor: pointer;
    transition: 0.3s;
}

    .btn-login:hover {
        background: #00c6ff;
        transform: translateY(-2px);
    }

.error {
    color: red;
    text-align: center;
    margin-top: 10px;
}