Wow, this is super cute! I love the vibe of this game. The pixel art and animations are fantastic.
- It might help to add a little bit of texture to the background. There are many ways to do this but it may help to just draw some a bunch of slightly soft alpha blurred circles of different sizes and positions if that makes sense. Or maybe like a few blades of grass to help give the illusion they are outside. Maybe a few trees or bushes the dogs can hide behind and play around.
- I want to keep playing but I'm not sure I understand the core mechanics. Generally what I think would make sense is... try to keep the food bowl full, sometimes a dog runs away with it, try to brush all the dogs, keep all toys in play as much as possible. It might be kind of fun if instead of throwing the balls off screen there are walls around the edges of the screen and the balls bounce off. That way you dont loose track of whats going on.
- Adding a high score tracker would add some replay value to entice players to come back for a better score. You could even link that to unlocking more stuff like varieties of dogs and toys.
- Maybe it's just me but I am finding the music a little jarring. Part of this could just be playing with zzfx a bit more to get better samples. A simple thing that could help is just making all the sound lengths shorter and reducing the volume to prevent it from getting too loud. You might even play around with a drum beat too. Weird idea but it could be fun if like yoshi you hear the drum beat only when holding an object.
- The font you chose looks great except there are some thin horizontal lines showing through, I think this is not LittleJS related but the font itself.
Keep up the amazing work, I will check back and see how you continue to improve it!