Fix snake movement

[Thomassteers]

What: This PR changes ________ by ________.
Why: This matters because ________.
Verified: I verified this by ________. I expected ________. I observed ________.
Status: This PR is (ready for review / a draft). Next step is ________.
Examples that count:

• I ran ________ and the tests passed.
• I reproduced the bug before, then confirmed it’s fixed after, using these steps: ________.
• I recorded / screenshot the behavior before and after.
• I checked the browser console and confirmed there are no errors during ________.

[patorjk]

What's up with all these PRs? I'm not opposed to looking at them, but it's rather strange to see so many at once out of no where.