This guide will show you only one possible way to beat the requested time of 18 second for the particular world. It's only a short guide, because there isn't too much to say.

As warning - the achievements 16, 23 and 35 are rather easy to gather than 55, which is a tough nut.

World 16 has many solutions to get the achievement. I will present you one way, but all others are nearly the same. Jump off the start platform and search the shortest way through the red objects to fall into the end portal or to grab the end platform to swing into the end.

Turn 180° at the start and jump off to fall by the red tube.

Half of the way turn again 180° and move always forward to fall by the red ball.

At least you will see the end portal. Try to fall into the end or grab the end plate from the lower side to swing into it.

Jump backwards from the start and grab the start plate to speed you up.

Grab the second wall at the right and steer to the right while swinging.

Grab the red cube at the edge and fly into the end portal.

The easiest 'Split Second' achievement. Jump at the start backwards, grab the start plate and swing into the end portal.

This was the hardest achievement for me from the 'Split Seconds'!

Jump off the start, grab the red wall and swing over between the red wall at the right and the transparent one. Your angle have to be right to land behind the wall (from above). Turn 90° right and grab the wall. If you're not in the correct angle you will swing in a round and you can restart. Use your speed to grab the last wall to fly high above the portal to fall into it. Sound easy? It isn't! Try it on your own.