Finwick is a pleasant, low-difficulty platformer with polished, nicely executed 2D graphics and (surprisingly) an engaging story. You're working as a postman during summer break, a job that apparently involves the skills of a special forces soldier -- leaping about, swinging on ropes, and so on.
The initial tutorial is a tad silly -- I think we know how platformers work -- but introduces the story well enough. The difficulty ramp is slow but steady, with enemies appearing only later. Puzzle-solving is at least as important as platforming skill, but the levels are purposefully designed so that you can never get stuck -- you'd just have to climb back up and try again or the like. There's quite a variety in terms of the challenges and visual look of the levels; on the whole, it's a nice game, if not something that will pose major challenges to those who grew up with a NES.
The first 25 levels are free, but there's a $6 charge for the rest (some 79 in all).