This is a game based on tiles! You can remix it and change the tile (in the costume of the second sprite) and all the tiles will change. I added triangles now! Move using the arrow keys. This also is half scrolling, half normal platformer. The player moves, as well as the background, giving it a cool effect. Also, I added a terrain generator! If the terrain goes too low, then it disappears, but I think I can fix that.
I will add this to the Environment Game: https://scratch.mit.edu/projects/490549870/ because I think this solves the problem that the background was of limited size - it was one drawn costume. Tiles are also a drawn costume, but they are small, and the background is made up of many of them. Problem solved!