Basic game, but I see a lot of potential for this one. I'd be curious to see how it would play from a top-down perspective where you can see the neighborhood laid out similar to a maze or mini-map style. It wouldn't require more advanced graphics, but would make the gameplay more complex because the player must decide if they should go up/down/left/right instead of just left/right.
It'd also be interesting if there was a probability that you got more or less candy from some houses. It could add an extra sense of reward and break up the repetitiveness of going to each house.
I love the time limit and I think it added some excitement to it all. In the future you could tie in the time limit to a story element. Like get as much candy as you can grab before the nightfall, or before the moon rises, or before Halloween ends. You can still have the same countdown timer, but changing the wording of what it's counting down to may add more depth to the game.
Keep at it!