<!DOCTYPE html>
<html>
<body>
<button id="countBtn">刻む（+2）</button>
<p id="display">0</p>
<button id="resetBtn">リセット</button>
</body>
</html>
let count = 0;
const btn = document.querySelector('#countBtn');
const display = document.querySelector('#display');
btn.addEventListener('click', function() {
count = count + 2;
display.textContent = count;
});
const resetBtn = document.querySelector('#resetBtn');
resetBtn.addEventListener('click', function() {
count = 0;
display.textContent = count;
});