It's a nice game but it looks like you didn't set it to capture the arrow keys, so if I move with arrows the entire browser screen scrolls. If you have time to edit it before the Jam deadline, the API docs describe key capturing at
https://photonstorm.github.io/phaser3-docs/Phaser.Input.Keyboard.KeyboardPlugin.html
and it looks like it would just be a matter of adding a addCapture() function to your code so it should be a quick fix. I used createCursorKeys() in my game which I think handled capturing automatically IIRC so I can't just paste my own code. This looks like a really nice game so I'd hate to see it downrated because of arrow keys scrolling (I'm using Chrome on Windows but I don't think that matters).