It's a very good title if you like physics-based mechanics, but the game doesn't exactly involve a lot of physics puzzles. For me, that was a good thing, because I am personally not a huge fan of pure physics puzzles games. They tend to feel kind of shallow.
Rochard's two biggest uses of physics are A) Catapaulting heavy objects on top of enemies to kill them, and B) a wide variety of anti-gravity navigation situations.
Enemies can be shot directly. Or you can throw heavy crates on top of them. Or---when applicable---you can break/pull the floor out from underneath them so that they fall to their death or land in an electric field. You can hold a crate in front of you at such an angle that enemy laser fire is deflected off the crate and ricochets into other enemies (but this requires a little bit of luck and is hard to execute intentionally). You can use your gravity gun to redirect mounted lasers into enemies to kill them. Later in the game, just like Half-Life 2, you can power up the grav gun to pick up the enemies themselves and throw them. You also receive three grenade types throught the game: a grenade that bounces and has a timed explosion, a grenade that sticks to a surface and has a detonated explosion, and a grenade that sticks to a surface and causes whatever it's touching to float into the air. Experimenting with all the different ways to kill enemies is one of the funnest aspects of the game, and successfully killing them with crates or other environmental hazards does not get old.
The game's puzzles often involve "switch" puzzles that change the colors of force fields. Blue lets everything pass through except crates/fuses. Red lets everything pass except for Rochard. Orange lets everything pass except for gunfire/explosions. White does not let anything pass. You will often have to exchange fuses and flip switches to create a path for Rochard or other objects through a maze of force fields. Other puzzle elements include gravity reversal switches (i.e. flipping between walking on the floor and ceiling), elevators, and doors. Often you will need to use crates and fuses to complete a puzzle and you'll have to figure out how to make a short supply of these objects go a long way. Suffice to say, the puzzle variation is great. The puzzle difficulty ranges anywhere between cakewalk and moderate. (With the exception of the Hard Times bonus levels. Those get much trickier.)
The anti-gravity stuff is pretty fun to play with too. If anti-gravity is on, you can pick up a crate, jump into the air, then launch the crate to send yourself flying through the air in the opposite direction. This includes jumping and firing a crate at the floor to launch yourself higher. One upgrade to the grav gun gives you an ability called "G-Swing". If zero G is on, this ability lets you jump into the air, then latch your grav beam onto certain fixed objects and slingshot yourself around the environment.
The only complaints I can make about this game are as follows:
1) In the very late levels when the difficulty starts to spike, the game starts to periodically break one of the golden rules of game design, which is this: "Don't subject the player to a challenge that they could not possibly overcome or recognize the solution to without dying first." The primary way the game does this is through "think fast" type situations. There will definitely be times when you'll walk through a door and so much ♥♥♥♥ comes at you all of a sudden that you get boned before you have time to figure out what is even happening.
2) Skyler's fake English accent. No offense to Lani Minella. She's worked on a lot of games, and I'm sure she's great to work with. But there are plenty of real English people in the world, and there is nothing distinctly English about Skyler's character. She could have just as easily been American. The team should have hired someone who actually HAS or can actually DO an English accent or just had Lani use her normal American voice. I hate to be so blunt to nice people doing honest work, but that accent was.... quite bad.
3) The grav gun has a tendency to aim-correct toward objects the player is PROBABLY aiming at but are targeting just a little too wide. In a lot of cases, especially early in the game, this is nice and makes the gameplay a lot more slick. However, later in the game the screen gets super cluttered with enemies, turrets, crates, bots, and platforms that you'll find yourself depserately trying to target X with your beam, but you keep latching onto objects A, B, C, D, E, F, and G instead. When this gets paired up with a "think fast" type situation, it leads to a certain degree of annoyance. Thankfully, this only happens a few times, and mostly in the late game.
A good little title that deserves more respect.