Paul and Percy are trapped on different sides of the wall. They can jump one brick or push one. They need each other to escape, only if both of them are at the portal, they can go to the next level. Pay attention though, sometimes one can help the other. Paul can push a brown brick through to Percy's side so he can continue. That is handy when Percy is stuck and can't jump two bricks at once.
Use the arrow keys. Use the space bar to switch from Paul to Percy and the other way around. Use the Z to go back one step and the R to restart the level.