It's a time management series that has developed a storyline with a developing plot that is actually interesting — not amazing, but at times surprising! I adore this game. I have played through it numerous times.
The Angry Birds franchise is addictive, but Bad Piggies is a hilarious, very well-done physics-driven, fairly open-ended invention game. Invent some crappy jalopy, then get it where it needs to go. You make it, the game breaks it, but as long as the "vehicle" makes it to its target, it often doesn't matter, and just serves to entertain.
I confess that I'm a bit of a fan of Paul Burkey, but this is a bit of brilliance. It looks like a re-skinned Boggle or something, but it's more clever and insidious than that, due to the "helpful" clues at the bottom — and the fact that those words that you found fifteen levels ago are still unavailable for reuse. You will shred through the levels, faltering only occasionally, and then faceplant.