As you can see by my playing time, I beat the whole game and in no case I would recommend this game.
Don't get blended by the graphics and buy Crazy Machines 1, Crazy Machines 2, The Incredible Machine or if your kid is just 6 years old Crazy Machines 1.5.

There are 3 terrible terrible mistakes in this game:

1) Inconsistent Physics: Imagine an object is flying on the left side of the screen. It always has the same trajectory, but if you place an element on the bottom right corner, which doesn't interfere with the other object, suddenly the trajectory changes and making it often impossible/very difficult to finish the task.

2) The grid on which you place your elements is way too big, causing a lot of unnecessary trouble. Imagine your idea/plan is absolutely correct, but you cannot execute it, because the laserbeam misses your mirror by 2 length-units, but you can move the mirror in the grid only by 10 length-units, causing the beam to miss your mirror again. This makes a lot of trial&error work necessary, even though it could have been easily avoided. In no other Crazy Machines game this was as annoying as here.

3) And that is the absolute deal-breaker here. You get punished if your solution is more intelligent than the default solution. The rewards are not task-based (the less you use, the better), but instead path-based. This means you have to place objects the way the game thought for you. Because if you don't, the trajectory of objects might be different and you won't be able to collect the cogs in the level. This is such a horrible design choice, I can't imagine why any sane developer would make this.

There is also something other bothering me and that was the "help". By looking at the shape of the background you can instantly see what object has to be placed. For example mirrors belong onto circle-shaped wood and generators on square-shaped wood. This dumbs the game down and no, that's not suitable for very young children, because Crazy Machines 1.5 makes it right. In that game are easier tasks, and more puzzles in between, so the difficulty doesn't rise too fast, but it does not dumb the puzzles down.

Stay away from this game and don't bother playing it. Get the other games I listed in the beginning of the review.

Very fun game once you figure out what you are supposed to be doing. Sometimes you get stuck from going foreward which can be aggravating. It can still be fun.

This game is boring and really less fun than the first one.

If you're a science guy, you will love this game. If you're not a science guy, you will still enjoy the game but it may take some time to beat the levels because they are very well made. You can see that the developers have a very rich imagination when you look at the puzzles. To complete puzzles you have to cause a chain reaction with different devices and toys, like toasters, gears, fans, etc...

It's a fun game, with a good soundtrack and it gets harder the more you play it. If you like difficult puzzles where you actually have to work for to find a solution this game is for you.
I recommend.

This and the other Crazy Machines games are lots of fun for my 5-year-old daughter and I. She learns about simple physics, and we both like problem solving contraption games. Elements is probably my favorite of the bunch, with a decent interface and graphics, and the professor isn't making comments all the time about your progress like at least one of the other Crazy Machines games. The puzzles in this one aren't too tough so far, but we're not very far in yet. I really appreciate that some puzzles have a quick solution, but have a way to get a better bonus if you want to keep at it. This lets my daughter choose how much we work on each puzzle. Again, lots of fun.