This level features a very high-placed pipe and a concentrated collection of goo hanging from a string
And even more goo below the string.
Start as usual by creating a high-yield goo facing downwards towards the other goo
And extend yourself downwards by simply making a slim box-design. Gravity is already with you so there's not much trickery behind this one
After reaching all the way to the bottom, the sleeping goo will wake up and climb upwards onto your rope, joining the other goo's
Sometimes you'll have to create an extra rope to get the really sleepy ones that are far away, don't sweat it
Now drag the camera upwards and start off by making a 3-4 string connected center slime. Take your time placing this one as it's the core of your tower
Now do the usual triangular constructs, forming boxes
Do not underestimate the distance of the pipe, leave plenty of space for alternative building space
After some building, you will see the pipe in all its glory.
Continue the box design until you get close to the muzzle
Place a final slime to make an effective hanger so that your entire tower won't plunge, losing all your progress
After placing the hangar, all your goos should eventually climb themselves up on the top. Leave some time for the AI to figure out a way upwards
The feature you unlocked can be described as a "Sandbox" mode where all the extra goo you've collected is accumilated in a special level with a secret at the very top of the stage. It can be found in your world menu.