The game is titled Gravity Falls: Legend of the Gnome Gemulets and it will be a platforming adventure style title. The game uses the UbiArt engine, which was behind games like Rayman Legends and Child of Light.
The game is sticking to the source material and will include the main characters Dipper and Mabel from the show as main characters in the game. The two will be discovering things within the wilderness of Gravity Falls much like the show. The shows creator, Alex Hirsch, is also heavily involved in the production of the game including creating the art assets.
As for actual story, the game revolves around a strange supernatural force that the twins need to fend off to save the town. Players can switch between the two characters with Dipper being a close range combat character and Mabel being a distance attacker.
You can check out the trailer and see what you think!