Good mechanic, good level design and good execution of ideas, what can be said negatively about this game? Only tiny things that are obvious to the devs, there is a tutorial that comes after the mechanic is implemented and the portals not signaling where they go, but they already know that.
A thing that would benefit the game is a marker showing where the cube will fall before i release my key, many runs end because i go a spot over or under my target, i dont think the arrows are help enough, it should be clearer.
The level design is excellent as previously discussed but some levels make use of a lot of moving enemies that makes the level more like chaos theory with the solution is just brute forcing your way with different tries instead of thinking about it, i think restricting it to 1 or 2 and complementing with a static enemy would make for more engaging levels (maybe even one that teleports between two places or one that turns on and off like a gate, just throwing that out there.)
Theme, you can only move in each direction once unless you get a hourglass, it fits and the entirety of the game is based on that.
Originality, not a crazy concept, there are plenty of puzzle and platform games where you can only move in one direction but havent seen being it done with all four.
Final thoughts, i went deep on what little nuggets i would change because i love this game, it might not be exciting or the most fun but is engaging and compelling, if they add more levels, keep building on it and create a mobile version i can see tons of people glued to the screen for just one more level. I know i would get lost in it while on the toilet and dont lie, you would too.