.smmp-form {
    max-width: 400px;
    margin: 20px auto;
    display: flex;
    flex-direction: column;
}
.smmp-form input {
    margin-bottom: 10px;
    padding: 8px;
    font-size: 16px;
}
.smmp-form input[type="submit"] {
    cursor: pointer;
    background: #0073aa;
    color: #fff;
    border: none;
}
.smmp-error { color: red; }
.smmp-success { color: green; }