The most common beginner instruction is "make me a to-do list". It can do that, but there's an 80% chance the result isn't what you pictured, and then you spend ten rounds fixing it.

A good instruction has three parts: goal (what to build, for whom), acceptance criteria (what "done" looks like), and constraints (what must or must not be used).

做一个待办清单网页，给我自己在手机浏览器上用。

验收标准：
1. 能输入一条待办并回车添加
2. 点一下能标记完成，完成的划掉
3. 刷新页面后数据还在（用浏览器本地存储）
4. 手机竖屏下按钮够大、不用横向滚动

约束：只用一个 index.html，不引入任何框架和外部库；界面简洁，浅色背景。