The Great Ghoul Duel is not a bad game.
It's nice to go to Google, intending to search the answer to a simple question, like 'is Central America part of North America or South America?' and get distracted by one of their 'doodles,' maybe learning something interesting in the process and returning to your original quest. Today's doodle is a little different. It's the kind of thing that will distract you for hours if you aren't careful.
It's called The Great Ghoul Duel and it's a 4-on-4 online multiplayer game, that combines capture the flag and Pac-Man and snake to make an addictive new experience. You, as a ghost, start out in your own base (either green or purple) and then venture out into the halls of a mansion to collect little blue flames, which attach to your ghost-avatar's hindquarters and trail behind you in a line, and which you have to bring back to your base to score points for them. If a player on the other team runs into your tail, they steal it. This is frustrating, to say the least, but also fun.
Google has made games as doodles before but never a multiplayer one. The reason for this one to be put out on halloween is likely that Google is trying to promote their open source matchmaking software called Open Match.
To play the game, go to Google.