GPT-5.5 vs GPT-5.6 Luna for vibe coding

- Add labels and live output for better accessibility.
- Validate non-negative bill amounts before calculating.
- Replace inline click handler with scoped event listener.

```html
<label for="bill">Bill</label>
<input id="bill" type="number" min="0" step="0.01" required>

<label for="pct">Tip %</label>
<select id="pct">
  <option>10</option>
  <option>15</option>
  <option>20</option>
</select>

<button id="calcBtn">Go</button>
<p id="out" aria-live="polite"></p>

<script>
const billEl = document.getElementById('bill');
const pctEl = document.g…

- Add explicit labels for bill and percentage controls to improve accessibility.
- Validate bill input and constrain it to nonnegative currency values.
- Replace fragile implicit element globals with explicit DOM lookups and `textContent`.

```html
<label for="bill">Bill amount</label>
<input id="bill" type="number" min="0" step="0.01" required>
<label for="pct">Tip percentage</label>
<select id="pct">
  <option>10</option>
  <option>15</option>
  <option>20</option>
</select>
<button onclick="calc()">Go</button>
<p id="out"></p>
<script>
funct…