Gravity is the most important game feature in-game. Otherwise you would be going nowhere. Its very important in the starting levels, because some of them don't have propelling items and so need to rely on the force of gravity. Gravity is most likely to be Newtonian, because wood and iron boxes fall at the same velocity, the weight doesn't matter, the air resistance does.
Maybe not intentional, some objects in the game show effects of it. Take King Pig and Freckles for instance: King Pig is a lot heavier than Freckles and a Lot bigger (or fatter). But unexpectedly King Pig falls a bit slower than Freckles, as shown in this video of Pigeneering. The best example is the Umbrella, it slows your vehicle dramatically.
Some parts are flexible, other are very stiff, and others even fragile. Flexibillity is a very important physic when on hilly terrain. Springs are intended for solving this problem, but there other solutions:
- Wood is fairly flexible and bending, but it can break easily if it gets too much punishment.
- Ropes are far the most flexible, but also the weakest.
- Springs are flexible and strong, but can be stuck in a sharp piece of rock in some levels. It also conducts engine power, unlike ropes. In fact,if you put a spring between two vehicles, it will count as one, but ropes don't.
Its also very important. Without velocity you are fully not going anywhere. Engines are designed for this. Velocity doesn't only mean speed, velocity is just movement.
Can be very annoying. Wheels are made to solve this. But in the Little Pig Adventure Sandbox and The Road to El Porkado, however is ice, which has nearly no friction and you can slide safely over the ground. Friction makes the most parts snap off. The alien variant for the metal box makes it have no friction, like ice ground in levels.
The When Pigs Fly episode is all about it. Simply going upwards. You can do it with balloons, rotors, propellers, airplanes, and more.