This 3x21 map is a modified part of one of my old projects.
It's meant to be fairly difficult, and there aren't too many checkpoints, so this isn't recommended for people who don't want to waste their time.
VVVVVVCE is required to play this map, and there are a few features in this that come from there.
There are two trinkets that you can try to discover.
Finally, I did add a time trial for this map if you're crazy enough to do it (my best time is ~11 min, with 200+ deaths)
Link: http://www.mediafire.com/file/yj35bsh06a1kddo/horizontaltower.vvvvvv/file