The concept for this game is really fun and I think you've chosen good, cohesive graphics for it. It took me a while to figure out how to even place a green slope. Ultimately I wish time progressed faster, or could be chosen to progress faster, as it gets a bit tedious after a while. I really wish there was a way to remove misplaced slopes. Sometimes I really didn't understand why certain pieces wouldn't connect, and so mistakes felt very punishing.
Some audio would be nice, and an indicator of where I am placing tiles down as I hover over them!