I really enjoyed this! It's a good example of how simple building blocks can combine into more complex puzzles. Some of the later levels were easier than I expected, but overall the difficulty level was enough to keep me thinking without getting stuck for too long.
The one thing I did struggle with a bit was that in a few levels, the order in which blocks execute their actions is key to the solution, but the order is not really clear. In those cases, I just had to use trial and error to nudge things into running in the order that I needed.