This is really cool, the idea to rewind orders is great :) I really had to think of my strategy when playing.
I did run into a few bugs, the orders thing started showing multiple orders as selected, and sometimes the movement/shooting indicator would show up on multiple units at the same time.
I wonder if it would be interesting if you could see the enemy's order list? This would add a planning aspect to it that you'd try to counter what they're doing. Just a thought, no idea if it makes sense :)
Overall a real interesting take on a turn based strategy game!