Your game doesn't keep focus on itself, so when I use the arrow keys to move the whole page moves up and down. Might suggest using WASD for movement to prevent this in future, or figure out what the cause of the lack of focus (using Windows 10 and Chrome for reference).

Animation wise, you probably want to centre the body for Left/Right so that when you change direction it doesn't feel like the body doesn't lurch from one side to the other.