Canvas is a Half-Life 2 Ep 2 modification that, as mods go, is one of the most impressively produced efforts you are likely to see. It tells the story of a girl with psychic powers, her psychically animated/possessed teddy bear, and the disappearance of her father, which the pair must investigate. Canvas is a 3D puzzle game, where the protagonist and her companion bear must use their powers to overcome obstacles and defeat enemies. Intriguingly, it's also set within the worlds of various paintings, which they must enter to unravel the mystery.
The teaser is below, and it's genuinely worth watching.