

Lingo ($6.99/$9.99) is an incredible exploration and word puzzle game. It also has a few excellent custom maps such as Duolingo and Liduongo.
A sequel (Lingo 2 $9.99) just released and is also excellent. It changes how puzzle rules are presented, making them playable in either order. It’s a more polished experience though, so playing the first game after would probably feel like a step backward.
Both combined is $15.58. That doesn’t include the excellent expansions for either game though.
They are the only portal-likes (chamber-based player movement puzzlers) that I’d place on the same level as the Portal games.