I loved it! Reminds me of Just Shapes and Beats, which will hopefully come out someday. I would consider making the difficulty curve a little steeper. This is the magic kind of game where failing is fun and makes me want to come back for more instead of frustrating. I think you should try to take advantage of that and make the earlier levels a little more challenging.
Very glad to see those spikes have retracted into the wall since the beta. :P
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