The regular walls will bounce you off if you hit the base of them. But keep in mind that if you catch the front of them as they are rotating, they will send you flying way off the side of the stage and kill you. You can collect coins which can allow you to purchase new circle characters. If needed you can watch a free ad video in order to earn three more coins. Quests will give you two coins apiece for completing them. To get the highest score possible, stop focusing on the coins and start focusing on simply getting to the next circle. Also, if you sit on one circle for too long you die automatically.