Incorrect (Too much JavaScript):

// app/components/signup-form.gjs
import Component from '@glimmer/component';
import { tracked } from '@glimmer/tracking';

class SignupForm extends Component {
  @tracked email = '';
  @tracked emailError = '';

  validateEmail = () => {
    // ❌ Reinventing email validation
    if (!this.email.includes('@')) {
      this.emailError = 'Invalid email';
    }
  };

  handleSubmit = (event) => {
    event.preventDefault();
    if (this.emailError) return;
    // Submit logic
  };

  <template>
    <div>
      <input
        type="text"
        value={{this.email}}
        {{on "input" this.updateEmail}}
        {{on "blur" this.validateEmail}}
      />
      {{#if this.emailError}}
        <span class="error">{{this.emailError}}</span>
      {{/if}}
      <button type="button" {{on "click" this.handleSubmit}}>Submit</button>
    </div>
  </template>
}