Zak is a neat little platformer that should take under 15 minutes to complete once, up to maybe an hour if you decide to earn the "no deaths" and "no kills" achievement for each stage. It's not particularly hard and there are plenty of checkpoints, so pretty much anyone can enjoy it regardless of their platforming abilities. It tells the story of a boy in a dystopian sci-fi world who gains a mysterious ability and breaks out of the prison-like compound he's been living in. The pixel art is simple but well done. The chiptune music is arranged such that it plays like one continuous track through the course of the game, which feels very dynamic.  And honestly there's just something satisfying about whacking mutant rats with a pipe.