Okay, I just beated the lvl and I think that even if it's a good lvl it's not that "hard" to beat.

I loved the mechanic of traspassing the wall with the javelin.

Btw, I think that i cheesed the final. If you take the debris part they give you in the gas elevator and you create a javelin, you can beat the lvl without going througth the last puzzle.

I'd give you a good 7/10 or 8/10, funny mechanics ^^