Found my way out of bounds after collecting the hypercube closest to the one way door area on the left of the map.
I managed to keep going left by jumping up from the area underneath there, kept going left, jumped and I have now fallen past the starfield in what appears to be the bottom-left of the map.
Otherwise, this game is brilliant! Lots of fun and reminds me somewhat of FEZ, which is one of my favourite games of all time. Good job :D