Nice one
I love the graphics and smoothness of the animation on this. It felt really nice and fluid. The controls were simple and easy to grab hold of. The idea was very impressive. Most of the time games that require 'clones' of yourself don't happen in real time - but this does happen in real time and you can move along side your fellow boxmen. Very nice implementation.
Timing is indeed a very big problem with games like these. I'm actually one of those people who enjoy bits of timing elements in games, but the timing window in some of the levels was just way to small. One slight mistake or slight hesitation in movement would cost the entire level. And sometimes levels had to be 'set up' and it was very time consuming. I suggest opening the time window a little. Don't eliminate it altogether, just give more allowance for errors. There's a fine line between interestingly challenging and stupidly frustrating. It's up to you to find that line.
Also I think there can be some slight tweaking with the landing space of the boxmen. It was slightly difficult to judge when jumping on the poles because they were almost exactly my size and even if I was slightly off I'd fall off completely. Usually platformers have an allowance at the edge of every platform for characters to stick out a little - just a little. I felt like it needed a bit more of that in this game, especially the level with the jumping on the thin poles.
I'd definitely love to see a sequel with more levels and perhaps new positions where my boxmen react differently. Maybe a difference between a walking and running boxman. Or a jumping on - as in jumping on the spot.
Good work with this.