A short, linear game. Luminous Horizon is the 3rd installment of the Earth and Sky series and it helps to be familiar with the first two to follow the story.
The game allows you to control two characters, brother and sister, both with super power suits, "Earth" and "Sky." A command "change" allows you to instantly change between them. Earth has super-strength and near invincibility as his special powers, and Sky is able to fly, fire electrical bolts, and create fogs.
The story truly has the flavor of a comic book, with colorful graphical "kapows," and numerous storyline and dialog cliches taken straight from superhero comic books. The humor in the game is based on making fun of these cliches. A link to a comic book feelie, which provides background info for those who forgot details from or haven't played the other two games, for the game can be downloaded.
The puzzles themselves fit in well with the superhero theme. I don't think it's too much of a spoiler to say that many of the puzzles are solved by using your team's superpowers and action-comic logic. Some of the puzzles are very easy, and some are more difficult requiring wandering back and forth until a "eureka" moment arrives. None of the puzzles are super hard or overly complicated, and talking to your sibling will give progressively bigger clues if you get stuck.
The game is well written, and far as I can tell, bug-free.