Well done Double Fine.
The story is simple enough. Become the big brother or sister and take your sibling along trick or treating and get home without incident or your grounded. Not long after the adventure begins, things go badly and your sibling is kidnapped. This is the motivation to see things through to the end as no one wants this to happen to their little brother or sister. Candy is the all mighty dollar and its to be found everywhere by whacking mail boxes, trash cans, piles of leaves etc. But the villians want this candy as badly as you and you have to trick or treat every house n every area to get to the next area and closer to rescuing your brother or sister. But seeing things through to the end will have you wearing a costume and transforming into a giant Shockwave (of Transformer fame) looking robot, or a black shrouded ninja, or even a....colorful unicorn? Yep.
The gameplay becomes strategic when your arsenal of costumes become bigger and battles will eventually require some strategy.
Exploration is simple enough and never overwhelming. Exploring will net you most of the materials for your costumes and of course some will come by part of the story.
Nothing too challenging and just rewarding enough to make this a worthy addition to your arcade collection.