This is a really cool idea! Good ramp in difficulty and showing the new blocks you place
As you mentioned it would be really nice to have a restart button as I had to refresh the game a couple of times. I don't know if it would make it too easy but also a highlight or preview of how far the arrows make you fly would be nice too!
Also I know there wasn't a lot of time and this is more work, but it would be nice to have a confirm before starting the level - as sometimes I misplaced blocks but couldn't undo my actions
This is really promising though and a lot of fun to work through :)