class MyButton extends HTMLElement {
  constructor() {
    super();
    this.textContent = this.getAttribute('label') || '点击我';
    this.style.padding = '10px 20px';
    this.style.backgroundColor = '#007bff';
    this.style.color = 'white';
    this.style.borderRadius = '4px';
    this.style.cursor = 'pointer';
  }

  connectedCallback() {
    this.addEventListener('click', () => {
      alert('按钮被点击！');
    });
  }
}

customElements.define('my-button', MyButton);

class MyCard extends HTMLElement {
  constructor() {
    super();
    const shadow = this.attachShadow({ mode: 'open' });

    const wrapper = document.createElement('div');
    wrapper.innerHTML = `
      <style>
        .card {
          border: 1px solid #ddd;
          border-radius: 8px;
          padding: 16px;
          background: #f9f9f9;
          font-family: sans-serif;
        }
        h3 { margin-top: 0; color: #333; }
      </style>
      <div class="card">
        <h3>${this.getAttribute('title')}</h3>
        <slot></slot>
      </div>
    `;

    shadow.appendChild(wrapper);
  }
}

customComponents.define('my-card', MyCard);

<template id="my-modal-template">
  <style>
    .modal {
      display: block;
      position: fixed;
      top: 0; left: 0;
      width: 100%; height: 100%;
      background: rgba(0,0,0,0.5);
      justify-content: center;
      align-items: center;
    }
    .content {
      background: white;
      padding: 20px;
      border-radius: 8px;
      max-width: 500px;
    }
  </style>
  <div class="modal">
    <div class="content">
      <slot></slot>
      <button id="close">关闭</button>
    </div>
  </div>
</template>

<script>
class MyModal extends HTMLElement {
  constructor() {
    super();
    const template = document.getElementById('my-modal-template');
    const content = template.content.cloneNode(true);
    const shadow = this.attachShadow({ mode: 'open' });
    shadow.appendChild(content);

    this.shadowRoot.getElementById('close')
      .addEventListener('click', () => {
        this.style.display = 'none';
      });
  }
}
customElements.define('my-modal', MyModal);
</script>