I love Bad Piggies though. I just felt that should be stated, so if this review sounds one sided, that's probably why. I'll try to keep it fair anyways. In short summary though, I heartily recommend this game for just about everyone. It's hard not to be entertained by the cartoon outcome of the game, and building the many contraptions, then seeing them in action brings about a simple joy that should not be missed.
In Bad Piggies, the gameplay breaks down to this. You're given a level screen, with an exit, and a blank area of a certain size at the starting area. The goal is to use the pieces you've been given in that level to build a machine that can transport the pig(which you must place on the machine) to the exit.
The levels also often have side objectives like collecting crates, getting to the exit in under a certain time, or even some more complex ones like delivering a large pig that won't fit in a crate on the machine.
One really cool thing I like is that you don't need to do all the objectives at once. If there's a crate and a time to beat, you can get just the crate with one machine, and when you get the time later, the game won't take away your crate even though your second solution didn't hit the crate on it's way. This really makes the objectives optional, and since you can build a machine just for one of the objectives, the design team can make some really diabolical side objectives without being limited to making them all be possible in one run.
The parts you have to build from range from standard wooden wheels and crates(which link together into shapes automatically), to more crazy stuff like single shot soda rocket launchers and springs. (Springs are one of my personal favorites just because they are so hard to use effectively but often hilarious when used wrong.)
The fun of the game, besides designing stuff that doesn't fall over, comes from hitting start, and then using your machine to get to the exit. Many of the parts are interactive, meaning they are gadgets you choose to "fire off" using buttons along the bottom while the puzzle is running. This means that to win the level you not only need to build something useful, but you also need to practice using it to solve the level.
Bad Piggies makes full use of a physics engine for all the parts involved in the vehicle. What this means is that every machine you built has a concept of center of gravity, weight, and of course, how strong the individual pieces are when it crashes or falls down off a ledge.
As you can imagine, the results of all this are often pretty funny, even, and especially, if your machine doesn't work. You'll have just as much fun watching your failed attempts accidentally fall apart halfway through the trip, or just falling over wrong at the start, as you will when you finally "get it" and move on to the next level.
The pig will also react rather hilariously both while building the parts and when running the machine. Place a TNT by him on the building phase, and he'll cringe knowing the solution is going to probably involve that exploding at some point. Well, until he decides you know best and goes back to smiling. Drive him fast, and he'll put on a big grin no matter where the machine is actually going. Send him too fast, and he suddenly changes to a scared look seconds before your machine crashes into a wall. The designers simply put a lot of effort into making the characters living, breathing, and with their own simple attitude, and it really shows. Pig is both disturbingly aware of his surrounding contraption while it's built and blissfully unaware of the near future of his doomed vehicle in motion. It's hard not to fall in love with the character's simple, forgetful, trusting, cartoon mind. The look of excitement and faith in success when you launch him and then sudden shock as the machine falls apart and sends him flying for the fifteenth time in a row is a classic cartoon humor that never gets old.
Where Bad Piggies truly shines though is in the creativity allowed in the solutions. A lot of these type of vehicle building games have characters that take damage from crashes, or require your machine to never break at all. Bad Piggies has a simple, yet amazingly fun solution to this frustration. All you need to do to finish the level in Bad Piggies is to get the pig to touch the exit. The pig is indestructible, so even if your machine explodes on the final slope down, you'll still win if the pig tumbled into the exit. This leads to some pretty funny solutions, and rewards you for adding more chaos(and thus fun) to the solution instead of punishing you for it.
The first couple of levels teach you how things work, and the parts are introduced one by one so that you can practice and master each one before moving on. But don't think this game is easy, the game quickly builds up to a more difficult level and by level 10 or so the amount of pieces and possibilities becomes downright diabolical. Many of the levels will give your mind a serious workout as you try to figure out what machine is ideal for crossing the terrain, much less how to complete the side objectives.
That's not to say the game is super hard to understand, aside from special challenge levels, most levels follow a simple theme in what they expect you to do. It's a masterful balance of instantly grasped concepts, and difficult to find solutions. In my book, that's basically the way puzzle games should work.
A couple of depth adding things really help flesh out the game. Do well enough in the regular levels, and you'll unlock more parts for use in Sandbox Mode. Sandbox Mode gives you a large build space and a level to explore. The only goal of this mode is to grab the crates, there's no exit and the game saves each crate once you hit it. This mode helps add a lot of length to the game as you can build pretty much whatever you like and see how it works as a vehicle.
As you progress in the main game's side objectives, your collection of "toy parts" increases, allowing you to get more crates in Sandbox Levels, but more importantly, allowing you to build more crazy rides and see how they work(or more often why they don't). Because the parts for Sandbox don't carry over into the levels themselves, the puzzles in the main game keep their challenge even as you unlock new parts.
And of course, no review would be complete without mentioning the music and sound effects. The music is incredibly catchy and doesn't get annoying(good when levels can take up to 5-15 minutes to figure out), and the sound effects fit right in. It all sounds like an upbeat happy cartoon, which is often in stark contrast to what your machines are doing(that is, blowing up). But the audio really helps highlight and add to the humor of the whole game, and helps to keep you from being too frustrated when things don't work out like you planned. You'll want the volume up the entire time you are playing, even though everyone will give you really weird looks when they hear the pig squealing in glee followed by dynamite and various bouncy sound effects.
There are a few minor things that I felt could use some improvement, but nothing particularly game breaking.
The building interface itself is very solid, but on the android touch screen I found dragging things around a bit of a pain due to my larger fingers. The game allows touching the part and then a space on the machine to add a part, but the only way to take a part off is to drag it down to the part strip. Letting go of it partway results in "replacing" the part with something else. This could be easily fixed if there was a way of selecting "air" or "delete part" as a part in the part bin, so that tapping would erase the space tapped. This may be the fault of my touch screen instead of the game, but it's such a common touch screen problem in touch driven games that it feels silly there isn't a simple "delete part" tool. (There is a button to delete the whole machine, but that doesn't help remove just a single part.)
Another thing I have mixed feelings about is that the game only saves the last built machine for each level. This is actually really helpful for puzzle mode, since if you have to quit halfway through a level your half built contraption will be there for you when you get back. But in Sandbox Mode levels, I really wish there was a way to save the contraption layout, so you didn't have to destroy your current contraption to build a new one.
Last, the game really needs a "replay my solution" button, and a way to save the solution for a level. Since the solutions rely on both having a machine built and on driving the machine properly, it can be really tricky to recreate the exact timing you activated the gadgets. I'd really like a way to "save" a replay, so that when I showed my friends how I finished levels, I didn't have to take several attempts to get parts like bottle rockets to activate right. This could open a whole new social aspect of the game if it was combined with a youtube uploading feature or some other way of sharing replay files. At the very least, I wish I could hit a "play that again" button on the victory screen, instead of the current "restart level" button that gives me the same contraption but makes me have to press the buttons during play all over again.
One very important thing to note is that the game is not battery friendly. Even with the sound off, I found I can't play for more then a few hours before my phone's battery is drained over 50%. I think it's the physics engine to blame, and there's not much the developers could have done about it if that's the case, but it's worth noting you probably won't want to play this for a long period of time if you will need your phone later before getting to a charge station.
Overall though, Bad Piggies is anything but bad. It's really one of the best android games out there, it's cheap (or in the case of the Android market, free!), and most of all it's got the simple joy that old childhood cartoons bring combined with the creativity of an "Incredible Machine" type of game.
I must make one final note, and I kind of wish I didn't have to say this, but this is the result of a free market. When getting the game, make sure the app you get is from Rovio. The markets are currently flooded with quite a few "look alike" or "rip off" games, and none of them are as good or as high quality as the original game, nor are they from Rovio.
I think that covers everything I have to say on this game. Go get it, it's brilliant, pretty unique, and can stand on it's own even without the Angry Birds popularity hook.