Really nice idea and great use of a simple set of mechanics to come up with some complex level designs, but mein gott that difficulty curve! I broke 5 keyboards and went through 3 divorces to complete level 3...
I think part of the problem is that you have to press a direction before pressing space - I think the game might feel fairer if it allowed you to start holding space before pressing a direction key. Is there a particular reason it's implemented this way? It's probably not helped by Unity being locked to 60fps on web increasing the likelihood of both button presses being captured in the same frame.