Why Is the D Key Ignored Only in My SvelteKit Game?

First determine whether the browser is receiving the key at all. In DevTools, run window.addEventListener('keydown', e => console.log(e.key, e.code)) and press D. If no event appears, try disabling Brave extensions, using a private window, or testing in Chrome or Firefox. Also check whether D works in another input on the same page. Missing TypeScript annotations would not normally make one physical key disappear completely.

Narrow it down systematically: test a known-working commit, then use a binary search through the commits to find the change that introduced the problem. Also test on another machine or browser. That will tell you whether the cause is in the application, the browser, an extension, or keyboard software such as an input method.

The commit history suggests the D key may be a red herring. A later bug-fixing change altered how the event handlers are attached and stopped removing listeners. If the component keeps adding handlers during updates or remounts, you can get stale or duplicated listeners and confusing behavior. Make sure every addEventListener has a matching removeEventListener, ideally by defining the handler once and cleaning it up when the component is destroyed.