Anna Anthropy aka Auntie Pixelante aka dessgeega does, I suspect, enjoy confounding expectations. You don't get many developers who follow up S&M-themed platformers with a Thrust tribute (of a very loose sort) starring a hyper-cute, angel-winged pig, after all. While Mighty Jill Off was a wry, subversive examination of why videogame protagonists put themselves through a torturous amount of struggle to reach their objectives, When Pigs Fly is simply about learning to fly. Though the grating, tragic squeals of the pig upon both flight and death do make for something of a sadistic endurance test...
It's a tricky affair - the slightest brush against the scenery costing piggie his gossamer wings and throwing him back to the start of whichever tunnel'n'spike'n'lava-filled room you're currently in. Again - it's about learning to fly, and the precision, spatial and velocity awareness that involves. Pigboy can't walk, but can only drift left or right through the air once he's aloft, which is achieved by a tap upon the spacebar. The longer you hold it down, the higher and faster he goes - and it's that you have to master. The challenge is escalated by the rooms' growing complexity, requiring you to stay aloft for longer stretches or make split-second height adjustments, mercifully interspersed with the occasional gimme stage.
Come the end, you're rated in terms of how many accidents you caused the poor porcine to suffer. Whether you feel triumphant, annoyed or horribly guilty very much depends on you.
It's hard, it really is. Someone will say below that it's not and that the rest of us are a bunch of wimps, but it's hard. Sometimes to the point of frustration, frankly, which is perhaps a little surprising given Anthropy's extensive analysis of platformer design in the past, but then by sticking it on Newgrounds I guess she's talking to a wider audience than with her previous fare, and one that often enjoys bragging about mastering tricky webgames (and about the digi-medals that come with that). It's a charming and compelling extrapolation of single mechanic, however, and as such well worth honing your space bar skills with.
Play When Pigs Fly here. Oh, one very important thing: S turns off the squeals. You're going to wanna press that bad boy button pretty sharpish. Lovely music, though.