Ok I beat the main game and hard levels 1-4. I was going to give this a 4/5 until I played those hard levels. Yes, they are really hard. But they were beautifully designed levels. Level 3 was a good challenge. Level 4 was super fun. So 5/5, Fav'd. This is a beautiful game, and has made me laugh out loud.
I think a good way to improve this would be a current block section, which shows what block you have. Because it's not obvious, but let's say there is 3 green in a row. You get a green. 2 more to go. click. 1 more. Hit a red. It turns out if you click, you still have green. Sort of confusing.