There are certainly a lot of possible aspects to improve upon. Like: Did you notice you can - if you're fast enough - make a 180° turn? Even though you blocked the easy one, this can still happen.
Or what about the fact, that the fruit can spawn inside the snake? Another place you can improve the game. Also: Different levels with walls or maybe different kind of food to eat. Or make the usable screen wider than the visible one. There are plenty of options to take on this simple game. Good luck!