|Normal gameplay||Bridge Building|
| This level is a major plot point!
This level is a major level in the game. After you finish the level, you may be able to access other characters, minigames, and tunnels. Most of them also include a cutscene.
| You get an achievement!
This level has one or more achievements. The achievements are listed on the level infobox.
This is level 13 of the B-Tunnel.
Unlike the previous few levels, this one is quite easy. You just need to locate the crumbling tiles and know where to step in an emergency. You can also step on the thick heptagonal rings, which are three tiles long. The crumbling tiles don't all link, but it's still a good idea not to waste them.
After this level, a cutscene is activated.
After this level, the Child asks the Student about her lab coat in Level B-12. She says that there is no dress code for science as it is the form of forming hypotheses and disproving them. The Child gets bored. So the Student says that not all school science is boring. The Child says that he doesn't need science. The Student mumbles 'Oh, so that's why...' and says 'Let me get back to you on this.' More can be seen on the Story page.
There is an achievement that is present in this level.
It is called Straight to the End and the goal is to beat the level without changing gravity.