Very cute game! The animation/drawing is simple, but it fits really well with the tone of the entire game. I think the music is also a very nice touch and it surprisingly did a lot to set the mood for this pet game.
For critiques, I think having a little more interaction coming from the pet would've been nice. I really love the fact that the pet will look towards where your mouse is when you're playing with it, but I think it would've been really cool if it also hopped around and followed your mouse. Also, when eating its food, perhaps it could have a special animation or make some kind of sound to show that it's eating. These are things that would only add to the experience though, so if you want to keep the very simple feel and tone of this game, then I totally understand as well.
Also, I notice that when I press the food button after playing with the pet, the pink sparkles will continue to come out. I feel like having the sparkles just completely stop appearing after selecting the food button might be nicer and make the game feel a bit more polished.
But overall, this was a very stress-relieving game! Good job! :)