Great platformer. It's the third time I've played. For those who have a hard time in the sand (orange) world, Jump up to a high spot and place your mouse there. Your sprite doesn't move along the x axis so if you use that and jump accross the blocks at the top of the screen found at the beginning and near the end of this world, you can use your cursor as a guide not to jump off.
As for the game, like I said, it's a great platformer. However, when you only have the blue world left having completed the green and grey world, and just having completed the orange one, you are sent back to they grey world. I think this was mentionned but I just wanted to make sure you knew of this bug. But it's such a minor nuissance that I won't dock stars.