Throw the rock to reach the finish line which is portal, but be careful with the platforms. Some platforms will be moving or rotating, some wil try to drop you, some will throw you in a random way, and some wil make something strange you couldnt even imagine. Control the strength of your throw, because if it will be too weak you may fall, or you wont aim into platform or portal if it will be too strong. Collect coins and buy new stones in the shop. Each of them has its own benefits. And be sure there will be level where you better use certain stone.